Effects of different doses of acetylsalicylic acid on renal function in the dog

This study was carried out in order to examine the effect of increasing doses of intravenously administered lysine-acetylsalicylic acid (ASA) on renal function in dogs. The first purpose was to examine the acute effects on renal water and solute output. The second purpose was to correlate the para-aminohippuric (PAH) clearance measurements with measurement of renal PAH extraction and renal blood flow (RBF). After 7 mg/kg ASA (20-80 microgram SA/ml plasma) a decrease in sodium excretion was observed in all dogs. With increasing ASA doses, the urine sodium excretion declined to 23% of the control period excretion. Tubular reabsorption of free water increased 10%. A significant and dose-related decrease in PAH clearance was observed in all dogs, from 108.7 ml/kg ASA to 58.8 ml/min after 200 mg/kg ASA. The creatine clearance was unchanged. PAH extraction fell in all dogs, RBF (measured by flowmeter decreased 21% at the highest plasma SA levels, as compared with 46% decrease in PAH clearance. ASA seems to inhibit tubular transport of PAH. Inhibition of prostaglandin synthesis by ASA offers one explanation of the effects of RBF and sodium excretion.