Gentamicin nephrotoxicity in the setting of acute renal hypoperfusion

The purpose of this study is to assess interactions between acute renal hypoperfusion and aminoglycoside nephrotoxicity. One hour of renal hypoperfusion (55-60 mmHg; renal blood flow 1.6 +/- 0.13 ml/min) was created in rats by suprarenal partial aortic constriction. Gentamicin, 120 mg/kg, was given at the start of the hypoperfusion period. Rats that either received gentamicin alone or were subjected to hypoperfusion alone served as controls. Hypoperfusion alone induced mild S3 proximal tubular brush-border membrane blebbing, but it caused no enzymuria, azotemia, or tubular necrosis. Gentamicin alone induced no azotemia or tubular necrosis. However, gentamicin injected during hypoperfusion caused severe azotemia (blood urea nitrogen 94 +/- 16; creatinine 1.74 +/- 0.22 mg/dl) and extensive S3 proximal tubular necrosis without affecting renal perfusion. S1 and S2 tubular segments, the major targets of gentamicin toxicity, showed minimal damage. Hypoperfusion increased renal gentamicin uptake, but matching it in control rats induced no renal damage. In conclusion, gentamicin can precipitate hypoperfusion-induced acute renal failure. This effect appears to be due to an S3 cytotoxic effect, which converts sublethal ischemic S3 tubular injury into overt cell necrosis.