INFLUENCE OF SEX-DIFFERENCES ON THE RENAL SECRETION OF ORGANIC-ANIONS

The kidney's responsiveness to male sexual hormones has been often neg lected. Renal secretion of organic anions is higher in male than ill f emale individuals; as a consequence, most of the xenobiotics that are excreted from the organism through this pathway are eliminated more ra pidly by males than by female animals. To gain further insight into th is issue, we studied in vitro and in vivo characteristics of the trans port of p-aminohippurate (PAH), a suitable marker for this system, in male and female rats, under different hormonal conditions. Kinetics of PAH showed a shorter elimination half-time in male than in female rat s (t(1/2el): male = 16.2 +/- 2.1 min, female = 25.7 +/- 4.5 min, P < 0 .05). Castration of male rats increased t(1/2el) to a value similar to that of female rats (t(1/2el): orchiectomized rat = 28.1 +/- 7.1 min) . Testosterone treatment of female rats increased the elimination rate to a value similar to that of male rats. In vitro PAH uptake by renal cortical slices from intact male rats was higher than that by slices from orchiectomized rats. Kinetic analyses of PAH uptake suggest that the difference was caused by a lower number of transporting molecules in orchiectomized than in intact animals, whereas the transporting cap acity for each carrier was similar in male and in orchiectomized rats. Our results suggest that testosterone increases the number of functio nal carriers for PAH in the kidney.