The renoprotective effect of angiotensin-converting enzyme inhibitors in experimental chronic renal failure is not dependent on enhanced kinin activity

Abstract

Background. Angiotensin-converting enzyme (ACE) inhibitors have been shown to ameliorate the progression of glomerulosclerosis both in experimental models of uraemia and in patients with renal failure. It has not been documented, however, whether this is due to a decrease in angiotensin II generation or is a consequence of elevated local level of bradykinin. Methods. Morphometric investigation of renal tissue was performed in 5/6 nephrectomized (SNx) rats, i.e. untreated or treated with the ACE inhibitor ramipril (SNx-RAM), the B2 kinin receptor antagonist HOE 140 (SNx-HOE), or a combination of both (SNx-RAM + HOE) over 8 weeks. A further group of SNx received delayed treatment with ramipril from week 5 onward (SNx-RAMD). In addition, a sham-operated (SHAM) control group was studied. Results. Systolic blood pressure was significantly lower in both SNx-RAM and SNx-RAM + HOE groups compared to (untreated) SNx. The glomerulosclerosis index (GSI) was substantially higher in the (untreated) SNx group (0.24 ± 0.04) vs SHAM (0.02 ± 0.01). A significantly higher GSI was found in the SNx-HOE group (0.45 ± 0.08) as compared to (untreated) SNx. However, in the SNx-RAM, SNx-RAM-HOE, and SNx-RAMD groups, the GSI was lowered to a similar extent (0.1 ± 0.02, 0.09 ± 0.02, and 0.07 ± 0.01 respectively). In addition, a concomitant attenuation of tubulointerstitial damage was noted in all the above groups. Conclusion. Increased kinin activity does not appear to play a major role in the renoprotective effect of ACE inhibitors in the remnant kidney model.