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Annals of Clinical & Laboratory Science 35:54-65 (2005)
© 2005 Association of Clinical Scientists

Progression of Renal Damage in the Obese Zucker Rat in Response to Deoxycorticosterone Acetate-Salt-Induced Hypertension

Ryan G. Morrison1, A. Betts Carpenter2, Van L. Adams1, Elsa I. Mangiarua1, Paulette S. Wehner3 and William D. McCumbee1
1 Departments of Physiology, 2 Pathology, and 3 Cardiovascular Services, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia

Address correspondence to William D. McCumbee, Ph.D., Dept of Physiology, Joan C. Edwards School of Medicine, Marshall University, 1542 Spring Valley Drive, Huntington, WV 25704-9340, USA; tel 304 696 7366; fax 304 696 7381; e-mail mccumbee{at}marshall.edu.


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 Acknowledgements
 References
 
This study assessed the progression of renal damage in obese Zucker rats in response to deoxycorticosterone acetate (DOCA)-salt-induced hypertension. Renal damage was evaluated by light microscopy and urine analysis at weekly intervals during the developmental phase of DOCA-salt hypertension and once during the plateau phase 42 days after the onset of treatment. Decreased tubular function was evident by day 8, as indicated by a significant increase in urine N-acetyl-ß-D-glucosaminidase activity and glucose excretion. The tubular index, a measure of tubular damage, was significantly elevated by day 15 and continued to increase throughout the experiment. Glomerular damage, which was evident by day 8, was followed by increased urine albumin excretion by day 15. Only a few sclerotic renal glomeruli were apparent before the plateau phase; however, by day 42, approximately 50% of the glomeruli were sclerotic. Hyperplastic vascular changes were mild at day 8 and slowly increased in severity during the developmental phase. By day 42 the vascular changes were severe with some vessels so hyperplastic that their lumens were almost occluded. These findings show progressive changes in renal structure and function that begin as early as day 8 and increase progressively until severe changes are present at day 42, resulting in an end-stage kidney.

(received 8 October 2004; accepted 21 October 2004)

Keywords: hypertension, obesity, renal tubular damage, deoxycorticosterone acetate, glomerulosclerosis


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 Acknowledgements
 References
 
Data from multiple national surveys clearly demonstrate a dramatic rise in the incidence of obesity (a body mass index in excess of 30) in the United States over the past 25 yr [1–3]. Because obesity is a risk factor for multiple disorders such as type 2 diabetes, coronary heart disease, and hypertension [4], the progressive increase in the incidence of obesity is now a serious health concern.

Obesity is a well-established risk factor for hypertension; the incidence of hypertension in obese adults is almost 3 times that observed in non-obese adults [5]. Consequences of chronic hypertension include serious end organ damage, resulting in cardiac and vascular hypertrophy, stroke, and/or renal damage. In the kidney, hypertension may initiate renal damage or promote the progression of previously established renal disease [6]. Hypertension-associated renal damage has been reported in clinical [7,8] and experimental studies [9].

While much attention has been focused on the role of hypertension in progressive renal damage, less is known about the effects of obesity per se on renal structure and function. A recent retrospective study suggests that obesity by itself may promote the development of focal glomerulosclerosis and glomerulomegaly [10]. The glomerular changes in renal biopsies from this study were similar to those observed by Kasiske et al [11] and Shimamura [12] in work with the mature obese Zucker rat, a genetically obese animal that is an experimental model of obesity-associated glomerulosclerosis [13–16].

The obese Zucker rat may also be useful as an experimental model to assess the interaction between obesity and hypertension in the promotion of progressive renal damage. We have recently reported that obese Zucker rats exhibit enhanced sensitivity to deoxycorticosterone-salt (DOCA-salt)-induced hypertension [17]. Systolic blood pressure rose more rapidly and the magnitude of the hypertensive response was greater in obese rats treated with DOCA-salt than in correspondingly treated age- and gender-matched lean rats [17]. Marked glomerulosclerosis and tubulointerstitial damage were evident in kidneys of hypertensive obese rats at the end of the study, whereas DOCA-salt treated lean rats exhibited only modest changes in renal histology.

The objective of the present study was to use biochemical and morphologic measures to assess the temporal pattern of changes in the kidney of obese Zucker rats in response to a course of DOCA-salt administration. Biochemical abnormalities reflective of tubular and glomerular damage were seen early and progressively during the developmental phase of the hypertensive response. Likewise, changes in tubular, glomerular, and vascular morphology occurred early and continued to increase in extent and severity over the course of the study. The glomerular damage involved the development of mesangial hypercellularity with an endpoint of glomerulosclerosis. Progressive changes in the tubules included tubular dilatation, atrophy of tubular epithelial cells, and cast formation. Vascular changes were prominent, with progressive development of hyperplastic arteriolosclerosis that increased in severity, culminating in the appearance of plexiform lesions and nearly complete vascular occlusion by the end of the study.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 Acknowledgements
 References
 
Animals.  Eight-wk-old female obese (fa/fa) Zucker rats were purchased from Charles River Laboratories (Wilmington, MA, USA) and housed in the Marshall University Animal Resources Facility in plastic cages with wood chip bedding at an ambient temperature of 23±2°C and a 12 hr light/dark cycle. Rats were allowed to acclimate to this facility for 1 wk prior to entry into an experimental study. The procedures using rats were approved by the Marshall University Institutional Animal Care and Use Committee.

Experimental procedures.  Nine-wk-old rats were deeply anesthetized with a mixture of ketamine HCl and xylazine (45:5 mg/kg) and unilaterally nephrectomized under aseptic conditions. Following surgery, rats were allowed to recover for 2 wk before being subjected to further experimental manipulation. After the recovery period, the rats were familiarized with the blood pressure measurement protocol for an additional wk before the blood pressure measurements for the experiment were begun. Throughout the study, body weights were measured twice weekly and the systolic blood pressure (SBP) measured once weekly on conscious rats by tail cuff plethysmography using a programmed electrosphymomanometer with pneumatic pulse transducer and tail cuff (Narco-Biosystems, Houston, Texas, USA).

Deoxycorticosterone acetate (DOCA)-salt hypertension was induced by biweekly injections of DOCA (25 mg/kg, sc) suspended in corn oil. During the DOCA-treatment period, 1% (w/v) NaCl was added to the drinking water. All rats had free access to Purina rat chow throughout the study. Five randomly selected rats were not treated with DOCA. These rats were sacrificed at 1 day after the beginning of the DOCA-salt treatment (Day 1) to obtain kidneys for histological analysis.

Six days before the start of DOCA-salt treatment and at weekly intervals during the developmental phase of the hypertensive response, 6 rats were placed in stainless steel metabolic cages to measure food and water consumption and 24 hr urine output and to collect urine for renal function tests. The animals were given 1 day to adapt to the metabolic cages before measurements were made and urine samples collected. Urine samples were collected at 6- and 24-hr, with the 6-hr urine sample being collected in a cold container. Immediately after the collection periods, the urine samples were centrifuged and the supernatants stored at –20°C until analysis.

Analytical procedures.  The Bradford [18] technique was used to measure the total protein content of urine; the data were expressed as mg of protein excreted per 24 hr. Urine albumin levels were measured as described previously [17]. Briefly, aliquots of a 24-hr urine sample were diluted with 0.9% NaCl and separated by one-dimensional PAGE, using a 5% stacking gel and a 10% separating gel. Following electrophoresis, the gels were stained using a Silver Stain Plus kit (Bio-Rad, Richmond, CA) according to the manufacturer’s instructions and dried overnight. Protein band density was measured with a Molecular Dynamics personal densitometer and the intensity of each protein band was expressed in relation to the albumin standard run with that gel. Samples high in protein content were diluted with 0.9% (w/v) NaCl before electrophoresis, so that their densities would fall within the linear portion of a densitometric curve prepared with graded concentrations of an albumin standard. Results are expressed as arbitrary densitometric units times the dilution factor of the individual 24-hr urine sample.

Urinary excretion of a lysosomal enzyme, N-acetyl-ß-D-glucosaminidase (NAG), and glucose were used as indices of renal tubular integrity. To remove NAG inhibitors, the urine samples were fractionated on a Sephadex G-50 gel filtration column before being assayed for NAG activity by means of a colorimetric assay (Roche Diagnostics, Indianapolis, IN, USA). NAG excretion was expressed as mU of NAG activity per 24-hr. Urine glucose levels were measured using a Glucose Analyzer–2 (Beckman Instruments, Brea, CA, USA), with the results expressed as mg of glucose excreted per 24 hr.

Histological methods.  At weekly intervals, 5 randomly selected rats were deeply anesthetized with a ketamine HCL-xylazine mixture (45:5 mg/kg) and euthanized by exsanguination via cardiac puncture. Kidneys were removed and sliced into sections that were fixed overnight in 10% (w/v) buffered formalin. Each kidney was entirely sectioned, and 2 representative sections were subjected to standard processing and embedded in paraffin. Sections were cut at 2 µm and stained with hematoxylin and eosin (H&E). Thin sections were utilized to enhance morphologic detail. Slides were reviewed without knowledge of the experimental groups. Twenty-five glomeruli were examined in each section and the amount of mesangial expansion was graded as follows: "1" if the mesangial area was normal, "2" if the area was mildly increased, "3" if it was moderately increased, and "4" if it was markedly increased. Mesangial expansion scores were calculated for each rat according to the procedure described by Dworkin et al [19]. In addition, the percentage of sclerotic glomeruli was determined by assessing 25 glomeruli in each section and counting the number of glomeruli that showed sclerosis. Tubular involvement was assessed semi-quantitatively by determining a cast score and tubular index for each rat. Cast scores were obtained by counting the number of tubules with casts per 25 high power fields and the tubular index was determined by counting the percentage of tubules exhibiting tubular atrophy and/or dilatation per 25 high power fields. Both determinations were scored as follows: "1" if 0–25% of tubules were involved, "2" if >25–50% of tubules were involved, "3" if >50–75% were involved, and "4" if > 75–100% of tubules were involved.

Statistics.  Data were expressed as means ± SEM. Statistical analyses were performed using Sigma Stat statistical software (Jandel Corporation, San Rafael, CA, USA). Following normality and equal variance testing, comparisons between groups were made using one-way ANOVA and, afterward, a Dunnett’s test for multiple comparisons against the untreated control group. When sample sizes were unequal, a Dunn’s test was used instead. Three data sets failed the normality test and were subjected to Kruskal-Wallis one-way ANOVA on Ranks followed by Dunn’s test for multiple comparisons against the untreated control group. Values of p 0.05 w e re considered statistically significant.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 Acknowledgements
 References
 
In obese Zucker rats subjected to DOCA-salt treatment, systolic blood pressure increases progressively for about 4 wk (developmental phase) and then tends to plateau at severely hypertensive levels [17]. In the present study, changes in the morphology of kidneys from DOCA-salt-treated obese rats were assessed at weekly intervals during the developmental phase of hypertension and at one point 2 wk after systolic blood pressure reached a plateau. During the developmental phase, temporal changes in renal function were also monitored.

The 24-hr urine output was measured at weekly intervals and, as expected, DOCA-salt treatment caused a progressive increase in the total amount of urine excreted beginning soon after the initial injection of DOCA on day 0 (Fig. 1Go). At all time points after day 1, there were significant increases in urine volume, compared to control samples that were collected 6 days before initial administration of DOCA. The increases of urine volume were accompanied by corresponding increases in fluid consumption (Table 1Go).



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  		Fig. 1. The effect of DOCA-salt treatment on urine volume. For each collection period, rats were placed in individual metabolic cages for 48 hr. During the last 24 hr, urine output was measured. Urine samples were collected 6 days (day -6) prior to and 1 day after the initial DOCA injection (day 0) and at weekly intervals thereafter. Each point is the mean ± SEM for 6 rats (*p <0.05 vs data for day -6).

 

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  		Table 1. Body weights, food and water consumption, and systolic blood pressure before (day -6) and during the DOCA-salt treatment period (days 1-22) (mean ± SEM)
 
Randomly selected rats were sacrificed just prior to the start of DOCA-salt treatment and at weekly intervals thereafter. The remaining kidney was removed from each animal, sectioned, and examined by light microscopy using H&E staining. Thin sections from all time points showed significant changes within the tubules. The normal architecture of the tubules was progressively altered and characterized by tubular disarray, dilatation of the tubular lumens, atrophy of the tubular epithelium, and loss of epithelial cell nuclei (Fig. 2Go). Hyaline casts were noted in the tubules in numerous animals. Although they appeared to increase over time, the casts were focal in distribution and were not seen in all animals. For semi-quantitative assessments of tubular injury, a tubular index and a cast score were determined for each animal. The tubular index for kidneys from DOCA-salt-treated obese rats began to increase as early as day 8 and thereafter increased progressively during the developmental phase of the hypertensive response; statistical significance was reached by day 15 (Fig. 3AGo). Cast scores, in contrast to the tubular index, were not statistically significant until day 42 (Fig. 3BGo), although there was a trend toward increased values beginning at day 22. Changes in tubular function were also evaluated during the developmental phase of the hypertensive response. NAG activity, a sensitive measure of tubular integrity [20], peaked in the urine of DOCA-salt-treated rats at day 8 and remained significantly elevated compared to untreated controls throughout the collection period (Fig. 4BGo). Another measure of tubular damage is glucose excretion (Fig. 4AGo). Urine glucose excretion became significantly elevated by day 8 and increased progressively throughout the collection period.



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  		Fig. 2. Histological changes in the kidney tubules at the following time points: a-control, b-day 8, c-day 15, d-day 22, e-day 29, and f-day 42. Magnification 600x, except panel a, which is 400x. The lower power was utilized for the control kidneys (panel a) to allow assessment of a larger field and show the lack of histological changes.

 


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  		Fig. 3. The effect of DOCA-salt treatment on renal tubules. Tubular indices and cast scores were determined on H&E sections of kidneys. Each point represents the mean ± SEM of the tubular index (A) or cast scores (B) from 5 rats subjected to DOCA-salt treatment for the specified number of days. *p <0.05 vs untreated uninephrectomized controls (day 0).

 


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  		Fig. 4. Effect of DOCA-salt treatment on urinary excretion of glucose and N-acetyl-glucosaminidase (NAG). Urine glucose levels (A) and NAG activity (B) were assayed in 24-hr urine samples collected 6 days (day -6) before the first DOCA injection (day 0), 1 day after the first DOCA injection, and at weekly intervals thereafter. Each point is the mean ± SEM for 6 rats. *p <0.05 vs day -6.

 
Glomerular changes were assessed using both biochemical and morphologic measures. The 24-hr urine albumin excretion, an important measure of glomerular function, showed a statistically significant increase beginning at day 15 (Fig. 5BGo). In addition, total urine protein exhibited changes similar to those observed for urine albumin with a significant increase evident by day 15 (Fig. 5AGo). Light microscopic review of the kidney sections revealed increased glomerular cellularity, primarily in the mesangium, beginning as early as day 8 (Fig. 6Go). This progressively increased at all time points until day 29.



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  		Fig. 5. Effect of DOCA-salt treatment on protein and albumin excretion. Total protein (A) and albumin (B) levels were measured in 24-hr urine samples obtained 6 days (day -6) prior to the first DOCA injection (day 0), 1 day after the first DOCA injection, and at weekly intervals thereafter. Total protein is expressed as mg/24 hr. Urine albumin is expressed as arbitrary units/24-hr. Each point is the mean ± SEM for 6 rats. *p <0.05 vs data for day -6.

 


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  		Fig. 6. Histological changes in glomeruli at the following time points: a-control, b-day 8, c-day 15, d-day 22, e-day 29, and f-day 42. Magnification 600x, except panel e at 400x. The arrow in panel a points to a small vessel in the control animal. Panel e was taken at a lower power to show 2 glomeruli with mesangial proliferation.

 
No sclerotic glomeruli were observed in sections obtained from rats during the developmental phase of the hypertensive response. To obtain a semi-quantitative measure of the increased cellularity, a mesangial matrix score was determined. The mesangial matrix score was significantly elevated at 8 days of DOCA-salt treatment and continued to increase throughout the developmental phase of the hypertensive response (Fig. 7Go). Sclerotic glomeruli, which were not evident during the developmental phase, began to appear at the beginning of the plateau phase. Two weeks into the plateau phase, 50% of the glomeruli were sclerotic (Fig. 7Go).



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  		Fig. 7. The effect of DOCA-salt treatment on mesangial expansion and the formation of sclerotic glomeruli. Mesangial matrix scores were determined on H&E sections of kidneys. Each point represents the mean ± SEM for 5 rats subjected to DOCA-salt treatment for the specified number of days. The vertical bars represent the percentage of sclerotic glomeruli at the indicated days. Sclerotic glomeruli were not evident before day 28. *p <0.05 vs untreated uninephrectomized controls (day 0).

 
Renal sections at all time points were examined for vascular changes. Special attention was paid to the afferent and efferent glomerular arterioles along with the peritubular vessels. No vascular changes were noted in the untreated animals. Overall, both the glomerular arterioles and peritubular vessels showed hyperplastic arteriolosclerotic changes (Fig. 8Go). These changes were characterized by intimal thickening, caused by the proliferation of smooth muscle cells and concentric layering of collagen, and by progressive narrowing of the vascular lumens. Initially, the vascular changes were mild and focal. They slowly increased in severity and extent from day 8 through day 29 (Fig. 8Go). Marked findings were seen at day 42, with some vessels so hyperplastic that the lumen was almost occluded. Focal fibrinoid necrosis was evident in the luminal areas of the vessels; however, hyperplastic changes were most prominent. The hyperplastic changes were so severe that some vessels formed plexiform type structures (Fig. 8fGo). At this time point, renal damage was severe in all areas and constituted an end-stage kidney.



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  		Fig. 8. Histological changes in vessels examined at the following time points: a-day 8, b-day 15, c-day 22, d-day29, e-day 42, and f-day 42. Magnification 600x. Panel f shows the plexiform structures.

 

   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
Acknowledgements
 References
 
In the present study, DOCA-salt hypertension was used to assess temporal changes in renal function and structure associated with the development of hypertension in genetically obese rats. DOCA-salt hypertension has been used by several laboratories to study the interactions between hypertension and other factors that lead to the progression of renal disease. Janssen and associates [21], for example, demonstrated that the Goto Kakizaki rat, a model of non-obese type II diabetes, exhibits more pronounced proteinuria and tubulointerstitial damage when subjected to DOCA-salt treatment than age- and gender-matched rats of the parent strain. Investigators assessing interactions between Heyman nephritis and hypertension have also used the DOCA-salt model of hypertension and have shown that rats immunized with a renal brush border extract show increased sensitivity to the development of DOCA-salt hypertension, a greater degree of glomerulosclerosis and proteinuria [22], and an enhanced production of cytokines and growth factors that are thought to promote renal damage [23], compared to non-immunized rats that are treated with DOCA-salt.

Similarly, we have shown that obesity greatly exacerbates the hypertensive response and the degree of end organ damage associated with DOCA-salt hypertension [17]. Compared to lean littermates, the development of DOCA-salt hypertension is accelerated in the obese Zucker rat and the magnitude of the hypertensive response that is attained is markedly higher. Moreover, the degree of renal damage is significantly greater in obese rats than in lean rats [17].

Because they are inclined to develop renal injury in the absence of external manipulation, DOCA-salt-treated obese Zucker rats provide a good model for studying the interactions between 2 factors that independently promote the progression of renal damage: obesity and hypertension. To this end, it has been clearly demonstrated that the spontaneous development of glomerulosclerosis [11,12] and tubulointerstitial damage [24] is more frequent in Zucker rats expressing the obese phenotype than in age- and gender-matched lean rats. In these animals, the development of glomerulosclerosis is preceded by a significant elevation in urine albumin excretion and mesangial matrix expansion [11].

In the present study, obese Zucker rats subjected to DOCA-salt treatment exhibited histological evidence of glomerular, tubular, and vascular abnormalities early in the developmental phase of hypertension. Mesangial hypercellularity and enlargement of the entire glomerular complex characterized the initial glomerular response. This was reflected by a statistically significant increase in the mesangial matrix score by day 8 of treatment. At this point, the rats showed only a mild degree of hypertension with the average systolic blood pressure for the group being 143.8 ± 4.8 mmHg. The extent and severity of glomerular changes increased steadily over time. By day 29, the mesangial matrix score reached its maximum and sclerotic glomeruli began to appear in kidney sections. Also by day 29, the steady rise in blood pressure reached a plateau phase characterized by systolic blood pressures >195 mmHg. It was during the plateau phase that the number of sclerotic glomeruli increased dramatically.

The development of sclerosis is an end-stage pathological response to glomerular injury. The mechanism underlying the development of glomerulosclerosis in DOCA-salt hypertension has not been clearly defined, although there is evidence that injury to the glomerulus caused by a variety of conditions leads to excessive production of growth factors and cytokines by mesangial cells and the attraction of inflammatory cells that may promote this process [25].

Biochemical markers of the functional integrity of the glomerulus (urine albumin excretion), and tubules (urine NAG activity and glucose excretion) were also monitored during the developmental phase of the hypertensive response. Significant increases in urine NAG activity and glucose excretion were evident before there was a significant increase in urine albumin excretion, suggesting that, in the obese rat, the functional integrity of the tubules may be compromised more rapidly during the initial phase of DOCA-salt treatment, compared to that of the glomeruli.

Significant increases in urine NAG activity and glucose excretion also preceded a statistically significant increase in the tubular index. The tubular index, a calculation used to quantify changes in tubular morphology, was significantly elevated by day 15 and continued to rise steadily throughout the remainder of the study. In contrast, the cast score, which measures the presence of casts in the tubules, was elevated significantly only after the kidney had been chronically subjected (day 42 in the process) to severe levels of hypertension associated with the plateau phase of the hypertensive response. This observation, coupled with the findings that cast distribution was focal and that casts were not present in all kidneys during the developmental phase of the hypertensive response, suggests that cast formation may be a consequence of end-stage renal disease induced by prolonged exposure of the kidneys to severe hypertension.

A unique feature of the present study is that we were able to observe the progression of renal damage throughout the developmental phase and well into the plateau phase of the hypertensive response. Comparisons of our results with other studies, however, are limited to changes associated with the plateau phase, because most studies that addressed changes in renal morphology in response to DOCA-salt administration were terminated only after the plateau phase had been reached. In studies that were terminated after 4- to 6-wk of treatment, the effects of DOCA-salt administration on glomeruli, tubules, and small vessels of the kidney were qualitatively similar. The extent of the damage varies from study to study with the degree of damage to the kidney and the incidence of mortality in obese Zucker rats being comparable to the more severe responses reported for DOCA-salt administration [26–28]. Variations in susceptibility to DOCA-salt treatment have been attributed, in part, to factors such as age [27,28] or strain [29]. We observed that an obese phenotype also has a profound impact upon the response of rats to DOCA-salt administration. As shown previously [17], the degree of glomerular and tubulointerstitial damage in the lean Zucker rat treated with DOCA-salt appears to be relatively mild. In contrast, obese littermates of the same gender exhibit profound glomerulosclerosis, tubulointerstitial damage, and vascular injury when subjected to an identical treatment regimen.

The progressive changes in the glomeruli and tubules beginning at day 8 and slowly increasing during the development phase may provide a good model to study the chronic renal changes that occur with hypertension and obesity. In contrast, dramatic vascular changes that occur most extensively at day 42 may provide a good model for studying malignant hypertension. Hyperplastic arteriolosclerosis is associated with malignant hypertension, which often occurs in patients with existing benign hypertension. Although we did not observe the vascular hyaline arteriolosclerosis that can be seen in patients with chronic hypertension, we did demonstrate changes in the glomeruli and tubules, as noted above. The dramatic vascular changes observed at day 42, accompanied by a marked increase in both tubular and glomerular damage, suggest that the sustained and dramatic increase in blood pressure leads to an end-stage kidney.

In summary, we have used histological examinations and biochemical markers to assess renal changes associated with the development of hypertension in obese rats. By so doing, we have observed that (a) there is evidence of renal injury very early in the development phase of the hypertensive response when the level of hypertension is mild, (b) the degree of renal injury increases with the rise of blood pressure during the developmental phase, (c) the functional integrity of tubules in the kidney of the obese rat may be more sensitive to injury induced by DOCA-salt hypertension than that of the glomeruli, and (d) certain indices of progressive renal damage, such as glomerulosclerosis and cast formation, are only evident after the plateau phase of the hypertensive response has been reached. We conclude that the obese Zucker rat is a good model to study interactions between obesity and hypertension on the progression of renal damage.


   Acknowledgements
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Acknowledgements
References
 
This study was supported, in part, by the Cardiovascular Research Support Fund of the Joan C. Edwards School of Medicine, Marshall University. The authors thank Ms Brandi Hanshaw and Ms Beverly Pofahl for excellent technical assistance.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Acknowledgements
 References
 

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