Renin, prorenin, and renin gene expression in rats with acute nephrotic syndrome

Caffeine augments proteinuria in puromycin-aminonucleoside nephrotic rats

Several studies indicate that increased intrarenal adenosine concentrations may attenuate puromycin-aminonucleoside (PAN)-induced nephropathy in rats. The purpose of this study was to investigate the chronic effects of caffeine, a nonselective adenosine receptor antagonist, on renal function and structure in PAN-induced nephropathy. Animals were randomized to receive drinking water or 0.1% caffeine solution. PAN was administered in two doses to a subset from each group at 1 week (100 mg/kg, s.c.; Purom-1) and 15 wks (80 mg/kg, s.c.; Purom-2) after initiating caffeine treatment (PAN and CAFF-PAN groups). The remaining animals served as time controls (CON and CAFF groups). Renal excretory function was followed for 23 wks. Caffeine consumption significantly augmented PAN-induced proteinuria after both PAN injections (Purom-1 and Purom-2, p<0.05 and p<0.001 respectively; CAFF-PAN vs. PAN). In addition, caffeine potentiated the transient reduction in creatinine clearance (CrCl) induced by PAN. Caffeine consumption for 23 wks significantly reduced CrCl in conscious nephrotic animals (4.76 +/- 0.98 vs. 8.51 +/- 1.55 L/kg/day, CAFF-PAN vs. PAN). Seven days after both PAN injections, increased plasma renin activity was detected in animals that were consuming caffeine as compared with corresponding control groups (CAFF and CAFF + PAN vs CON and PAN, respectively). Eight weeks after the second injection of PAN, acute measures of renal hemodynamic and excretory function were compared in anesthetized animals and renal samples were analyzed for histological changes. In PAN-rats, caffeine treatment for 23 weeks significantly reduced inulin clearance (0.28 +/- 0.09 vs. 0.57 +/- 0.12 mL/min/gr kidney. CAFF-PAN vs PAN, p<0.05), tended to increase renal vascular resistance (59.0 +/- 9.5 vs. 42.9 +/- 5.5 mmHg/mL/min/gr kidney, CAFF-PAN vs. PAN, p < 0.06), potentiated the development of more severe tubulointerstitial damage (tubular atrophy, presence of proteinaceous material, tubular dilatation, interstitial inflammation, interstitial fibrosis), and tended to increase glomerulosclerosis. In conclusion, this study indicates that caffeine adversely affects renal function in PAN-nephrotic rats, and that this effect may be due, in part, to increased activity of the renin angiotensin system.

Ascites fluid of nephrotic rats: sodium dodecyl sulphate-polyacrylamide gel electrophoresis protein pattern and the renin-angiotensin system

1. The concentration of renin and angiotensinogen (Ao) and the activity of angiotensin I-converting enzyme (ACE) was measured in the ascites fluid of nephrotic rats obtained 8 days after puromycin aminonucleoside (PAN) injection. 2. Ascites fluid, serum and urine proteins of these rats were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). 3. Renin, Ao and ACE were found in the ascites fluid and the percentage of the ratio ascites fluid/(plasma or serum) ranged from 5.9 to 9.9%. The electrophoretic analysis revealed that the ascites fluid contained low (Mr < 66 kDa) and high (Mr < 66 kDa) molecular weight proteins. Albumin and six proteins higher than 66 kDa were present both in the ascites fluid and in serum from nephrotic rats. 4. Data from the study suggest that some proteins in the ascites fluid, including renin, Ao and ACE, come from the plasma. It is possible that the loss of renin, Ao and ACE to the ascites fluid may be playing a role in the metabolic alterations of these three proteins in PAN-nephrotic rats.