The renin-angiotensin system and compensatory renal hypertrophy in the rat

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The Renin-Angiotensin System and Compensatory Renal Hypertrophy in the Rat

Angiotensin 11 (Ang Ii) may act as an angiogenic and growth promoting factor in different tissues. To assess the role of Ang I1 in compensatory renal growth following unilateral nephrectomy (UNX), we measured renin, angiotensinogen, and Ang II type 1 (AT,) receptor mRNA leveis, as well as Ang II receptor density, in two groups of Sprague-Dawley rats 7 days after either sham operation or UNX. Half of each group received either no treatment or an angiotensin-converting enzyme inhibitor (100 mg/dL captopril in the drinking water, initiated at the time of the intervention). Following UNX, the ratio of kidney weight to body weight (KWIBW) in untreated animals was greater than in rats undergoing sham UNX (0.46 2 0.01 17 0.37 2 O.Ol%, P c .Oll. Neither renal renin, nor renal or hepatic angiotensinogen mHNA levels, determined by slot blot hybridization, changed significantly after UNX. Ang II receptor density in glomeruli, determined using an ‘*%Sar’-lle’ Ang II in situ receptor binding assay on frozen kidney sections, did not change significantly after UNX, nor did renal AT, receptor mRNA. In captopril-treated rats, KWlBW was greater in UNX than in sham operated rats (0.44 t 0.01 u 0.37 + 0.010/c, P <

Rrreived September Y, 1Y9J. Accepted September 311.14%. From thr Divisions of Nrphrolog:j :;-I’V, MHH) .mJ Endocrinology (LAS, CAL, MS), Deturtment of Medicine, San Francisco General Hospital, University of California San Francisco, S.m Francisco, California. This work was supported by US Public Health Research Grants HL 11046 and DK 31623 from the National Institute> of Health, and by grant-in-aid 891124 from the Amcricnn Heart Associntion. Dr. Valentin was the recipient of fellowship awards from ICI-Pharma and the American Heart Association. California Affiliate, and Dr. SW!-! from the Italian Society of Hypertension and the Juvenile

.Oll, similar to results in untreated animals. Renal and hepatic angiotensinogen mRNA levels were not affected by captopril treatment and did not change further in response to UNX. Captopril treatment increased renin mRNA in both sham operated and UNX rats as compared with untreated controls, but had no significant effect on Ang IJ receptor density and AT, receptor mRNA; and no change was observed in either variable as a consequence of UNX. Thus, compensatory renal hypertrophy following UNX occurred in the absence of measurable changes in components of the renin-angiotensin system, and despite functionally significant inhibition of this system by captopril. These data do not support a critical role for Ang II in compensatory renal ii’! lY97 American Journdl ot hypertrophy. Hypertension, Ltd. Am J Hypertens 1997;lO: 397-402 KEY WORDS: Angiotensin 11, angiotensin converting enzyme inhibition, angiotensinogen mRNA, renin mRNA, AT, receptor, angiotensin receptor antagonists, captopril, hypertrophy, kidney, uninephrectomy.

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nilateral nepbrectomy results in growth of the remaining kidney through hypertrophy with only a small component of hyperplasia.‘-’ The mechanisms responsible for this compensatory response are not known with certainty, although a number of biochemical and molecular changes have been observed that could be inv01ved.‘-~ Among the earliest of these are alterations in the levels of cyclic nucleotides4 and an increase in phospholipid incorporation into cortical membranes5; protein kinase C activity also increases,6*7as does renal polyamine content.’ Subsequently, an increase in RNA content occurs, which includes the expression of genes encoding for pm-rRNA constituents, structural transport proteins, lo and proto-oncoproteins,” genes. ‘ok” Angiotensin II ( Ang II) binds to specific cell surface receptors,‘* activates intracellular signaling pathways associated with cell growth, and induces proliferation and hypertrophy of a variety of o~lls.“-‘~ The role of Ang II in cell growth has been studied extensively in vascular smooth muscle cells, where it has been implicated as a mediator of the abnormal growth of these cells in some models of hypertension.‘4,*9 Because many renal cell types respond to Ang II in vitro and possess appropriate intracellular signalling pathways, a growth regulatory role for Ang II in the kidney has been suggested.‘6.‘R In this study, we evaluated the components of the reninsngiotensin system during compensatory renal growth in Sprague-Dawley rats. In addition, we examined the hypertrophic response in animals in which Ang II generation was suppressed by administration of an angiotensin converting enzyme inhibitor. METHODS Experimental Design Male Sprague-Dawley rats (Ban&-Kingman, Fremont, CA) were housed in climate controlled conditions (20°C and 55% relative humidity with a 12-h light/dark cycle) and provided standard rat chow and drinking fluid ad libitum. Experiments were conducted according to two major experimental protocols.

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time of the intervention and maintained for the duration of the study. Seven days after either UNX or sham operation, the animals w?re killed by decapitation, and the kidneys were quickly removed, weighed, snap-frozen in liquid nitrogen, and stored at -80°C. Livers were also snap-frozen in liquid nitrogen. Experiment 2 The functional adaptation to UNX and the efficacy of angiotensin converting enzyme inhibition were assessed in 18 UNX rats, half of which received captopril, initiated 1 week before UNX. To determine 24-h water intake, urine volume, and the daily urinary excretion of sodium and potassium, rats were placed in metabolic cages on the day preceding the intervention and on the last day of the experiment; urinary sodium and potassium concentrations in 24h urine collections were determined by flame photometry (Instrumentation Laboratories Model 943, Lexington, MA). One week following UNX, rats were anesthetized with lnactin (Andrew Lockwood and Associates, Sturtevant, WI) and placed on a heated table to maintain rectal temperature at 37 2 0.5”C. Rats underwent tracheostomy to allow spontaneous breathing and were prepared for acute experimentation as previously described” Briefly, catheters were inserted into a jugular vein for infusion of solutions and a carotid artery for continuous measurement of arterial pressure with a Statham P23ID pressure transducer (Gould Instruments, Oxnard, CA) connected to a polygraph (model 7D, Grass Instrument Co., Qumcy, MA). After stabilization following completion of surgery, arterial pressure was recorded for 10 min. after which the efficacy of angle tensin converting-enzyme inhibition was assessed by determination of the pressor response to an intravenous bolus injection of 200 ng of Ang I (Sigma Chemical, St. Louis, MO). Arterial pressure was recorded for the next 10 min; the rats were then killed, and the kidneys removed and weighed. Slot Blot Analysis of Renin, Angiotensinogen, and AT, Receptor mRNA Total cellular RNA was isolated from frozen tissue by a modification of the guanidinium thiocyanate method” as described previously.” The rat renin clone was a kind gift of Kevin Lynch, University of Virginia and the AT’ cDNA probe a kind gift of Kenneth Bernstein, Emory University.23 Angiotensinogen, renln, and angiotensin receptor mRNAs were qumtitated by slot blot hybridization, as described previously.z4~ze Autoradiographs were obtained by exposure to Cronex x-ray film (DuPont, Wilmington, DE) with an intensifying screen at -80°C for 4 to 8 days and were scanned using a laser densitometer (LKB 2202 Ultroscan, Piscataway, NJ) for’quantitation.

Experiment 2 Rats 3 months old, weighing 290 to 340 g, were anesthetized with pentobarbital(50 mg / kg intraperitoneally, Abbott Laboratories, Chicago, IL). The right kidney was exposed using a drrsal approach and either removed (UNX; n = 14) or gently manipulated and left in place (Sham L1vX; n = 14); removed kidneys were weighed and processed as described below. The wound was closed and the animals allowed to recover. Among both the UNX and the sham UNX animals, half received no treatment, whereas the other half received an anglotensin converting enzyme inhibitor (captoprit; In Situ Ang II Receptor Assay The distribution and Squibb Institute for Medical Research, Princeton, NJ) density of Ang II receptors was assessed by a modifimdissolved in the drinking water at a concentration of Eon of the in situ autoradiographic technique of MenIO0 mg/dL. Captopril treatment was initiated at the delsohn et aI” as previously described.=

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Statistical Analysis Values are expressed as mean 2 SEM. Data resulting from scanner analysis are presented as arbitrary scanner units. Since no difference in any measured variab!e was observed between the left kidney removed at nephrectomy and either the left or right kidney removed at the end of the experiment in untreated sham UNX animals, the values from these kidneys were pooled together and considered as a control group. Student’s t test for paired or unpaired comparisons was used to assesssignificance within and between groups. A P = .05 was considered the minimum level of significance. RESULTS Experiment 1 Effect of UNX in Normal Rats In sham UNX animals, the weights of the right and left kidney were identical, and similar to the left kidney weight removed at the time of nephrectomy (Table 1 I. UNX was associated with a 23.3% 2 2.3% (P < .OOOl) increase in kidney weight, whereas body weight increased by only 3.7 z 2.1%. Consequently the ratio of single kidney weight to body weight (KM’/ BW) increased significantly (Table 1). Neither renal renin nor renal or hepatic angiotensinogen mRNA levels changed signiRcantly after UNX. In control kidneys, specific binding of ‘251-Sar’-IIes Ang II occurred in glomeruli and medullary var;c?llar bundIes, as reported pretiOUSiy, za and UNX had no effect on binding distribution. Neither glomerular Ang II receptor density nor renal AT, receptor mRNA level was altered significantly by UNX (Table 11. Influence of Angiotensin Converting Enzynle Inhibition OH the Responseto UNX Captopril treatment markedly reduced the pressor response to injected Ang I (Table 2 I. In sham operated rats, the ratio of KW/BW was not affected by captopril treatment as compared with untreated animals (Table 1 I. Following UNX, kidney weight increased by 20.4 2 1.2% (P < .OOOlj from a control value of 1.24 t 0.04 g. One week after UNX, the weight of the remaining kidney in these captopriltreated rats (1.50 2 0.05 g) was not different from the weight of the remaining kidney of untreated animals (1.53 2 0.03 g). Body weight increased by only 5.9 2 1.8%; as a consequence, KW / BW increased to the same extent as in untreated animals. Captopril treatment resulted in a four- to fivefold increase in renin mRNA levels and no change in either renal or hepatic angiotensinogen mRNA levels. AT, receptor mRNA levels and glomerular Ang II receptor density were minimally increased as a consequence of the treatment ( + 13% and +25%, P = NS and P = 0.064 respectively) (Table 1 I. Renin mRNA levels were slightly reduced after UNX as compared ‘with sham UNX animals, but were stiil signiftcantly greater than values from control and UNX untreated kidneys (Table 1) . As H as aIso observed in untreated animals, neither renal nor hepatic angioten-

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&3

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TABLE

2. EFFECT OF UNILATERAL NEPHRECTOOMY AND BLOOD PRESSURE IN CONTROL

-~

Water Intake, mW24 h Day -1 L’nitateral 35.6 2 1.1

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Day 7

~~

UV, mW24 Day -1

h Day 7

UNaV,

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meq/24

h

UKV,

meqb24 h

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EXCRETION,

MAP, Baseline

mm Hg

Day -1

Day 7

Day -1

Day 7

Post-Ang

1.62 2 0.29

1.42 -C 0.24

2.90 + 0.49

2.49 2 0.41

102 -C 4

144 + P

1.31 k 0.19

2.58 + 0.48

2.44 -c 0.40

93 -)_ 2

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II

nephrtutomy, untreated rats (n = 9) 34.2 2 2.1

15.0 t 1.1

15.1 i 0.8

Unilateral nephrectomy,captopril-treated rats (n = 9) 38.4 fr 2.0

41.8 + 2.4

16.1 i 1.3

17.0 ? 2.1

1.47 t 0.31

UNX.“’ Furthermore, angiotensin converting enzyme inhibition prevents the development of proteinuria and glomerulosclerosis after UNX when the treatment is initiated at the time of the intervention, but not when started later.3’ Captopril has beneficial effects in preventing functional and structural glomerular Experiment 2 The functional adaptation to UNX, damage in rats with nephron loss from renal ablaevaluated by the capacity of the remaining kidney to tion.“,‘5 Angiotensin converting enzyme inhibition increase electrolyte excretion, was preserved in capto- also suppressed accelerated growth of glomerular pril-treated animals as indicated by similar 24-h urinary cells of maturing kidneys both in vitro and in vivo excretion of sodium and potassium before and 7 days after UN?“; however, in that study, UNX was perafter UNX (Table 2). Because Ang II could have growth formed in young rats, so that the inhibitor could have promoting activity during the first hours following affected hyperplasia rather than hypertrophy. Ang II UNX before the rats started to ingest the captopril, we may also contribute to renal growth indirectly, as it evaluated compensatory growth in rats pretreated with potentiates the mitogenic effect of epidermal growth captopril for 1 week before UNX. Jn this group, the f actor in proximal tubular cells in culture.” Ang Ii ratio of KW / BW increased to the same extent as in itself has a hypertrophic effect on cultured mesangial untreated rats (from 0.37 + 0.01 to 0.42 t 0.01% and and proximal tubular cells ‘v’ that could be mediated from 0.39 -t 0.01 to 0.43 2 O.OY%,respectively). Thus, via stimulation of transforming growth factor-p.M Aldespite functional inhibition of the renin-angiotensin though the pattern of activation of early response system, compensatory renal hypertrophy took place to genes in the kidney after UNX is a matter of some a similar extent in both capiopril-treated and untreated controversy,‘“,“.‘7-‘9 Ang II induces activation of animals. proto-oncogene mRNA in cultured murine proximal tubule cells that resembles the pattern observed after DISCUSSION UNX?0z39 Such observations provide further circumUnilateral nephrectomy results in an increase in the stantial evidence in favor of a role for tang II in the weight of the remaining kidney primarily through a hypertrophic response, although the relationship of process of cell hypertrophy, with only a small compo- these changes in proto-oncogene expression to the hynent of hyperplasia.‘-’ Ang II has an established role pertrophy has been questioned.“” as a growth factor in a variety of tissue and cellular The results of this study provide evidence against factor in the systems. It has been shown to cause hypertrophy of a role for Ang JI as a growth promoting cultured quiescent rat aortic smooth muscle cells,“’ as development of compensatory renal hypertrophy in well as rat renal mesangial’” and proximal tubular”’ adult animals. Renal hypertrophy occurred in the abcells in culture. In addition, the renin-angiotensin sys- sence of activation of the renal renin-angiotensin system has been implicated in several forms of renal tem and &spite suppression of Ang II generation, growth. An increase’in dietary protein intake leads achieved by chronic captopril treatment. UNX did not to renal hypertrophy; accompanied by an increase in lead to a significant change in renin or angiotensinoplasma renin activity and renal renin KZNA?~ In dia- gen gene expression 7 days after UNX. These results betic rats, a high dose of enalapril blocks the enhanced are consistent with the observation of Rosenberg et renal hypertrophy and microalbuminuria induced by a1,31 who showed no change in renin mRNA Level sinogen mRNA levels changed significantly after UNX. Moreover, neither the density of glomerular Ang II receptors nor the level of AT, receptor mRNA was altered following UNX, similar to results in the untreated animats (Table 1).

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or plasma renin activity 7 days after UNX. Although activation of one or several components of the reninangiotensin system could have occurred at earlier time points, this does not seem likely: in rats in which both tissue and circulating levels of Ang II were likely to have been reduced shortly after UNX by treatment with captopril, renal hypertrophy occurred after UNX, just as in untreated rats, suggesting that angiotensin-mediated responses in the period immediately following UNX were not important components of the subsequent hypertrophic response. The efficacy of captopril treatment was con<.rmed by the marked attenuation of the pressor response to a bolus intravenous injection of Ang I. In addition, renal renin mRNA levels increased by four- to fivefold during captopril treatment, in agreement with a previous observation.40 Captopril treatment did not affect compensatory renal growth after UNX. These results are in contradiction to earlier studies showing a partial inhibition of compensatory renal growth following UNX by angiotensin converting enzyme inhibitors. Wight et a14’ showed that, in adult Wistar rats, enalapril treatment reduced compensatory renal growth following UNX. Dworkin et al” observed that both captopril and enalapril reduced compensatory renal growth in spontaneously hypertensive rats. Howevei, UNX in these studies of Dworkin and associates was performed in 6-week-old rats, an age at which both hyperplasia and hypertrophy would be expected to occur. In the studies of Wight et al in adult rats,*’ control animals l;.ldergoing UNX had increased renal protein apd DNA content 1 week later so that the protein:DNA ratio was unchar:n,ed. In enalapril-treated rats, DNA content, used as a marker cf hyperplasia, did not increase after UNX despite a large increase in protein content. Therefore, they concluded that converlmg enzyme inhibition interfered with hyperplasia but did not affect hypertrophy.4’ This interpretation is somewhat at variance with most of the work examining compensaiory renal growth, which has uniformly shown that this occurs primarily through a process of hypertrophy with at best only a small ( < 20% ) component of hyperplasia (reviewed in references l-3). Although we did not measure renal protein or DNA content, our data clearly show that functionally effective converting enzyme inhibition did not alter compensatory renai growth. The basis for the difference in our results flom those of Wight and colleagues”’ is not clear. Their treatment with enalapril was started 4 weeks before IJNX, whereas in our Experiment 2 studies, captopril was adminis,tered 1 week before UNX. It is difficult to imagine that this difference in length of exposure could modify the results, or that the two different converting enzyme inhibitors used had different actions. Rats in the study of Wight and associates4’ lost weight in the week following UNX, and it is possible

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that postsurgical 1,ypercatabolism modified their results in some way. In our present study, as well as in previous work from this laboratory,’ rats gained weight after UNX. It is also possible that converting enzyme inhibitors do block the hyperplastic component of compensatory renal growth. If so, this component must have been sufficiently small in our studies so as not to be detected by ihe methods we used. In summary, our results indicate that compensatory renal hypertrophy following UNX occurred despite inhibition of the renin-angiotensin system by captopril. These studies therefore do not support a critical role for Ang II In the development of compensatory renal growth following UNX. ACKNOWLEDGMENT The authors are grateful to Dr Zola P. Horovitz, BristolMyers Squibb Institute for Medical Research, Princeton, New Jersey, for the gift of the captopril used in thesestudies. REFERENCES I.

Fine LG: The biology 1986;29:619-634.

2.

W,sson LG: Compensatory growth and other growth responses of the kidney. Nephron 1989;51:149-184. Fine LG. Norman I: Cellular events in renal hypertrophy. Annu Rev Physiol 1992;51:19-32.

3.

of renal hypertrophy.

Kidney

Int

4.

Schlondorff D, Weber H: Cyclic nucleotide metabolism in compensatory renai hypertroehy and neonatal kidney growth. Proc Nat1 Acad Sci USA 1976;73:524-528. 5. Toback FG, Smith I’D, Lowenstein LM: Phospholipid metabolism in the initiation of renal compensatory growth after acute reduction of renal mass. J Clin invest 1974;5n:91-97. 6. Caramel0 C, Tsai P, Okada K, Schrier RW: Protein kinase C activity in compensatory kidney growth. Biothem Biophys Res Comm 1988;152:315-321. 7. Hise MK, Mehta Ps: Activity of calcium-sensitive phospholipid-dependent protein kinase C following nephron jnsc. Kidney Int 1989;36:216-221. 8. H&iphreys MH, Etheredge SB, Lin SY, et al: Renal ornitbine decarboxvlase activity, polyamines, and compensatory renal hypertrophy in the rat. Am J Physiol 1988;255:F270-F277. 9. Oulette AJ, Moonka R, Zelenetz AD, Malt RD: Regulation of ribosome synthesis during compensatory renal hypertiophy in mice. Am J Physiol 1987;253:C506c513. 10. Norman JT, Bohman RE, Fischmann G, et al: Patterns of mRNA expression during early cell growth differ in kidney epithelial cells destined to undergo compensatory hypertrophy versus regenerative hyperplasia. Proc Nat1 Acad Sci USA 1988;85:6768-6772. 11. Beer DG, Zweifel KA, Simpson DP, Pitot HC: Specific gene expression during compensatory renal hypertrophy in the rat. J Cell Physioi 1987;131:29-35. 12. Douglas JG: Angiotensin receptor subtypes of the kidney cortex. Am J Phy& 1987;253~F1-~7. 13.

Ray PE, Aguilera

G, Kopp JB, et al: Angiotensin

II re-

402

VALEhTIN

A/H-APRIL

‘Ff 4L

ceptor medi&i mesangial cc&

prc,Iiferation of cultured human I&&y Int 1991;40:764-771.

fetal

14.

Re B, Rovigatli D: New approaches to the study of the celiular bioI&y of the cardiovascular system. Circulation 1988;77fauppI II:Il4-117. 15. Norman J, B@+-Dezfooly B, Nord EP, et al: EGF-induced mitog+?sie in proximal tubular cells: potentiation by ang++&in II. Am J Physiol 1987;253:F299F309.

16.

Norman Jy: site r& of bhgiotensin II in renal growth. Renal PhysioI $iocbem 1991;14:175-185.

17.

Fogo A, Yos&Ia Y. Yared A, Ichikawa I: Importance of angiogeni6 @ion of angiotensin II in the glomerular grou th of m&ring kidneys. Kidney Int 1990;38:10681074.

18.

Wolf G, NeilPop EG: Angiotensin II as a rend growth factor. J Am $$ Nephtol 1993;3:1531-1540. Baker KM, f%‘i& GW, D&al DE: Cardiac actions of angiotensin II: role of an intracardiac renin-angiotensin system. Annt’ I& Pbysiol 1392:54:227-241.

19.

20.

21.

Valentin JP, & C, Muldowney WP, et ah Cellular basis for blunted JoIume expansion natriuresis in experimental nepFb&c sybdrome. J Clin Invest 1992; 90:1302-1312. Chirgwin JM, frzbyla BE, McDonald RJ, Rutter WJ: Isolation of PioIo&aIly active ribonucleic acid from sources enri&d in ribonuclease. Biochemistry 1979; 185294-5299.

22.

Sechi LA, G&in CA. Grady EF, et al: Tissue-specific transcriptiona\ regulation of insulin receptor gene in rats with streptpzotocin-induced diabetes mellitus. Diabetes 1992;$1:$113-111%.

23.

Murphy TJ, ,&#aflcier RW, Griendling KK, et al: Isolation nf a cD$\ encoding the type-l angiotensin II receptor. &at@ /991;351:233-236. Kalinyak JE, FerIn%t A]: Tissue-specific regulation of angiotensin.&!fl Ij\wA accumulation by dexamethasane. J Biol I&Z~ 1987;%2:460-464.

24.

25.

Kalinyak JE, Sgchi LA, Griffin CA, et al: The reninangiotensin &‘$m in stmptozotocin-induced diabetes in the rat. J p$ Sac Nephrol 1993;4:1337-1345.

26.

Sechi LA, G&m angiotensin &tee in the rat. D&tes

27.

Mendelsohn F&o, I@lan M. QuirIon R, et al: Localization of angioW& II receptors in rat and monkey kidney by in vitro autoradiography. Kidney Int 1987; 31(supp120,:S.4,0.5@.

28.

Se&

CA, Schambelan M: Cardiac reninin stfeptozotocin-induced diabetcv 1994;43:1180-1184.

LA, Gr’ady EF, Griffin

CA, et al: Distribution

of

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angiotensin II receptors subtypes in rat and human kidney. Am J Physiol l992;262.F236-FXO. 29. Anderson PW, Do YS, Hsueh W: Angiotensin II causes mesangial cell hypertrophy. Hypertension 1993;21:2935. 30. Wolf G, Neilson EG: Angiotensin II induces cellular hypertrophy in cultured murine proximal tubular cells. Am J PhysioI1990;259:F768-F777. 31. Rosenberg ME, Chmielewski D, Hostetter TH: Effect of dietary protein on rat renin and angiotensinogen gene expression. J Clin Invest 1990;85:1144-1149. 32. Whiteside CI, Thompson J: The role of angiotensin II in progressive diabetic glomerulopathy in the rat. Endocrinology 1989; 1251932-1940. 33. Beukcrs JJB, Van Der Wal A, Hoedemarker PJ, Weening JJ: Convertmg enzyme inhibition and progressive glomemlosclerosis in the rat. Kidney Int 1987;32:794-800. 34. Anderson S, Rennke, HG, Brenner BM: Therapeutic advantage of converting enzyme inhibitors in arresting progressive renal disease associated with systemic hypertension in the rat. J Clin Invest 1986;77:1993-2000. 35. Cartwright ME, Jaenke RS Effects of dietary protein and captopril on giomerular permselectivity in rats with unilateral nephrectomy. Lab Invest 1988;59:492499. 36. Wolf G, Mueller E, Stahl RAK, Ziyadeh F: Angiotensin II-induced hypertrophy of cultured murine proximal tubular cells is mediated by endogenous transforming growth factor-o. J Clin Invest 1993;92:1366-1372. 37. Kujubu DA, Normal JT, Herschman HR. et al: Primary response gene expression in renal hypertrophy and hyperplasia: evidence for different growth initiation processes. Am J Physiol 1991;260:F823-F827. 38. Oulette AJ, Malt RA, Sukhatme VP, Bonventre JV: Expression of two immediate early genes, Egr-1 and c-fos, in response to renal ischemia and during compensatory renal hypertrophy in mice. J Clin Invest 1990;85:766771. 39. Nakamura T, Ebihara I, Tomino Y, et ah Gene expression of growth-related proteins and ECM constituents in response to unilateral nephrectomy. Am J Physiol 1992;262:F389-F396. 40. Comer RA, Lynch KR, Chevalier RL, et al: Renin and angiotensinogen gene expression an3 intrarenal renin distribution during ACE inhibition. Airi J Finysiol lY88; 254:F900-F906. Wight JP, Basset AH, Le Carpentier JE, El Nahas AM Effect of treatment with enalapril, verapamil and indomethacin on compensatory renal growth in the raf Nephrol Dial Transplant 1990;5:777-780. 42. Dworkin LD, Grosser M, Feiner HD, et al: Renal vascular effects of antihypertensive therapy in uninephrectomized SHR. Kidney Int 1989;35:790-798.