Urine profiles and kidney histologic findings after intravenous injection of mannitol and iohexol in the degeneration phase of gentamicin nephropathy in rats.

RATIONALE AND OBJECTIVES

Previous studies have shown that iodinated contrast media may cause further renal dysfunction in tubulointerstitial nephropathy induced by gentamicin. The current investigation was undertaken to study whether the dysfunction after intravenous injection of a low-osmolar contrast medium is due to a chemotoxic and/or an osmotic effect.

METHODS

Urine profiles were followed for 3 or 9 days after intravenous injection of saline, mannitol, and varying dosages of iohexol (1, 2.5, 5, and 10 mL/kg body weight (BW); 350 mg I/mL) in 60 rats, in which intramuscular injection of 40 mg/kg BW gentamicin had been administered daily nine times. A seventh group of 10 rats was given 20 mg/kg BW gentamicin and 5 mL/kg BW of 350 mg I/mL iohexol. Another 10 rats injected with saline served as controls.

RESULTS

Both mannitol and iohexol increased the excretion of albumin and the enzyme N-acetyl-B-D-glucosaminidase (NAG) temporarily; the effect was independent of the dose of iohexol. There was a dose-dependent effect on the transient increase in excretion of the enzymes lactate dehydrogenase (LDH), gamma glutamyltransferase (GGT), and alkaline phosphatase (ALK); mannitol did not increase the excretion of these enzymes. In the group given 20 mg/kg BW gentamicin, only the dose-dependent effects of iohexol were seen. Neither various plasma components nor light/electron microscopy showed any changes that could solely be related to the contrast medium.

CONCLUSIONS

Iohexol produces transient renal effects in gentamicin nephropathy, which may be due to both chemotoxic and osmotic mechanisms.