Effect of duration of diabetes on the protection observed in the diabetic rat against gentamicin-induced acute renal failure.

We have previously shown that the rat with experimental diabetes (DM) of 4-6 months' duration exhibits complete functional and morphologic protection against gentamicin-induced acute renal failure. To assess the role of the duration of the diabetic state per se on the resistance to gentamicin, female Sprague-Dawley rats with diabetes of short (5 days, n = 7), intermediate (5 weeks, n = 5) and long duration (5 months, n = 7) were studied. Diabetes was induced by streptozotocin, 50-65 mg/kg b.w. i.v. Controls were identically treated sex- and age matched nondiabetic rats. The animals were kept in individual metabolic cages for 2 weeks and all received gentamicin 40 mg/kg/day for 9 days. Sham animals (DM and control) received Ringer's solution in place of gentamicin. Prior to gentamicin, plasma glucose levels and creatinine clearances (Ccr) were higher in the DM long duration group (619 +/- 25 (SE) mg/dl; 2.6 +/- 0.2 ml/min, respectively) than in the DM short (514 +/- 24; 2.0 +/- 0.1) and DM intermediate duration (442 +/- 30; 2.1 +/- 0.1) groups, while urine volume and glycosuria were similar. Following gentamicin the three control groups developed acute renal failure (maximal decrease in Ccr of 60 +/- 7, 72 +/- 9 and 71 +/- 7%, respectively; p less than 0.01 to less than 0.001), lysozymuria and acute tubular necrosis. There were no significant differences in the degree of renal impairment observed among the three control groups. In marked contrast, in the three DM groups these changes were absent and the renal cortical gentamicin content was lower than that of the control groups.(ABSTRACT TRUNCATED AT 250 WORDS)