Taurine modulates arginine vasopressin-mediated regulation of renal function

Taurine has been implicated in the regulation of arginine vasopressin (AVP) secretion, and we have previously shown altered renal excretory function i n the taurine-depleted rat. To further elucidate the role of taurine in AVP -mediated renal responses, the effects of an antagonist for renal AVP recep tors were examined in four groups of conscious rats: control, taurine-suppl emented. taurine-depleted, and taurine-repleted, Control and taurine-supple mented rats displayed similar and significant AVP receptor antagonist-induc ed elevations in fluid excretion. sodium excretion, and free water clearanc e but a marked reduction in urine osmolality. These effects are consistent with inhibition of endogenous AVP activity. By contrast, in the taurine-dep leted rats, the magnitude and the time course of drug-induced renal excreto ry responses lagged behind those of the control and taurine-supplemented gr oups. Further, baseline urine osmolality was significantly higher in the ta urine-depleted compared with the control or taurine-supplemented groups. Ho wever, after administration of the antagonist, taurine-depleted rats manife sted a delayed but more marked reduction in urine osmolality. thereby elimi nating the baseline differential that existed between the taurine-depleted rats and control or taurine-supplemented groups. Consistent with these obse rvations, plasma AVP was significantly increased in the taurine-depleted co mpared with the control rats. Interestingly, taurine repletion shifted all responses closer to the control group. Analysis of the data suggests that t he effect of the antagonist on renal excretory function is related primaril y to altered tubular reabsorption activity. These observations suggest that taurine modulates renal function, and, thereby. body fluid homeostasis, th rough an AVP-dependent mechanism.