POTENTIATION OF GENTAMICIN-NEPHROTOXICITY IN THE RAT BY INFUSION OF APROTININ

The present study was undertaken to examine a possible effect of aprot inin, a 6.5-kDa polypeptide with an inhibitory effect on proteolysis, on aminoglycoside nephrotoxicity. Experimental animals (female Sprague -Dawley rats, 175-200 g body wt) were treated for 4 days with 40 mg/kg gentamicin given ip at 12-hr intervals. Aprotinin (40,000 kIU per ani mal) was infused iv over a period of 8 days, using subcutaneously impl anted miniosmotic pumps. In protocol A, infusion pumps were placed 4 d ays before starting gentamicin treatment. In protocol B, pumps were im planted 15-18 hr prior to first gentamicin administration. In addition to rats exposed to both gentamicin and aprotinin (GAP), animals were treated with gentamicin ip + saline iv (G), saline ip + aprotinin iv ( AP), or received only saline by both routes of administration (C). All rats were terminated 4 days after the end of gentamicin dosing. One h our before sacrifice, 200 mu Ci of [H-3]thymidine was given ip to each animal in order to monitor cell turnover in renal tissue. The kidneys were analyzed with respect to (i) histopathological alterations and r enal dysfunction, (ii) aminoglycoside tissue accumulation, and (iii) t ubular regeneration (measurement of cell proliferation). In animals re ceiving aprotinin alone, histological examination of renal cortex on p araffin sections disclosed mild tubular injury with focal cell necrosi s. In plastic-embedded tissue, proximal tubule epithe hum was characte rized by the presence of numerous inclusions densely stained with tolu idine blue. At the ultrastructural level, these inclusions appeared fi lled with amorphous electron-dense material. In gentamicin-treated ani mals, cortical drug accumulation reached values higher than 0.3 mg/g r enal tissue, but a significant 30-40% decrease of gentamicin accumulat ion was noted in GAP groups, compared to G groups. Histological examin ation of renal cortex (paraffin sections) revealed the development of acute tubular necrosis in both G and GAP groups. Tubular injury was ac companied by mild renal dysfunction, as shown by the level of serum cr eatinine which was increased almost 3-fold in the G group, compared to C and AP groups. Aprotinin infusion produced a further increase of se rum creatinine, particularly in protocol A when it was 72% higher for the GAP group than for the G group. In both G and GAP groups, postnecr otic tubular regeneration was evidenced by determining the rate of DNA synthesis and the frequency of S-phase cells in renal cortex. Both me thods gave consistent results and showed a 8- to 13-fold increase of c ell proliferation in groups receiving gentamicin alone, compared to C groups. Furthermore, a significantly higher proliferative response was observed in GAP groups, in comparison with G groups. To conclude: (i) aprotinin alone induces in proximal tubule epithelium morphological a bnormalities suggesting the accumulation of peptide-like material; (ii ) aprotinin increases the severity of aminoglycoside-induced tubular n ecrosis (evaluated by the degree of tubular regeneration) and renal dy sfunction (assessed by the measurement of serum creatinine). (C) 1994 Academic Press, Inc.