Effect of anthracene-9-carboxylic acid on the renal function of the unanesthetized rabbit

Anthracene-9-carboxylic acid (9-AC) decreased the conductance to chloride in the isolated thick ascending limb of the loop of Henle and in the isolated perfused frog kidney (Greger, 1984; Oberleithner et al., 1983). The aim of this study was to study the in vivo effects of 9-AC in the unanesthetized rabbit. 9-AC decreased glomerular filtration rate, chloride and sodium clearances and urine volume. While glomerular filtration rate, chloride clearance and urine flow followed similar time courses for decreases and recoveries, and therefore seemed to be related, sodium clearance and fractional excretion of sodium showed an independent time course from the clearance of inulin and remained low throughout the experiment, suggesting a direct tubular effect. Values higher than unity for the fractional excretion of 9-AC, suggest that net tubular secretion of this acid occurs despite 9-AC is bound more than 80% to plasma proteins in the range of 10(-6) to 10(-3) M.