The effect of thromboxane A2 receptor antagonism on amphotericin B-induced renal vasoconstriction in the rat

Amphotericin B (AmB) is the drug of choice for most systemic fungal infections, but doses are frequently reduced because of nephrotoxicity. We investigated the role of thromboxane as a mediator for this nephrotoxicity. Vehicle or amphotericin (0.60 mg/kg) was infused into the left renal artery in four groups of rats, and renal plasma flow (RPF) and glomerular filtration rate (GFR) were measured. Group 1 received vehicle for 90 min. Group 2 received vehicle followed by a 30 minute AmB infusion which caused a significant and reversible fall in the RPF and GFR. Group 3 received vehicle followed by AmB infusion, but were infused with a bolus of ibuprofen (20mg/kg) 45 minutes before AmB. This group exhibited an insignificant attenuation in the fall in RPF and GFR. Group 4 received vehicle followed by AmB, but were infused with a bolus and continuous infusion of the thromboxane receptor antagonist SQ29,548. This group demonstrated an attenuation in the fall in RPF and a significant decrease in GFR compared to AmB control rats. In addition, the rat glomeruli were incubated with AmB (4ugm/ml). Supernatant levels of thromboxane B₂ were significantly elevated in the presence of AmB vs buffer alone. We conclude that the reduction in RPF and GFR observed with AmB infusion in the rat is partially mediated by release of thromboxane.