Role of sympathetic nervous system in hypotensive action of taurine in DOCA-salt rats.

Abstract

We tested the hypothesis that the antihypertensive effects of dietary taurine supplementation in deoxycorticosterone acetate (DOCA)-salt rats may be attributed to the suppression of sympathetic nervous system activity. In uninephrectomized rats treated with DOCA while receiving 1% NaCl solution for 2 weeks, systolic blood pressure was significantly increased as compared with that in control rats treated with vehicle suspension and tap water. Sympathetic nervous system activity was assessed by tissue norepinephrine turnover, which was determined from the rate of decline of tissue norepinephrine concentration after the administration of alpha-methyl-p-tyrosine, a potent inhibitor of the rate-limiting step of catecholamine synthesis. Cardiac and splenic norepinephrine turnover during either normal conditions or cold exposure (4 degrees C, 8 hours) were markedly increased in DOCA-salt rats as compared with control rats. Also, DOCA-salt rats had increased depressor response to hexamethonium bromide, a ganglion blocker. In contrast, supplementation of 1% taurine in DOCA-salt rats attenuated the development of the hypertension associated with the normalization of both the increased depressor response to ganglionic blockade and the accelerated cardiac and splenic norepinephrine turnover during either normal conditions or cold exposure. Taurine supplementation in control rats, however, had no effect on blood pressure or norepinephrine turnover during cold exposure. These results suggest that taurine supplementation suppresses sympathetic overactivity in DOCA-salt rats, thus leading to inhibition of the development of hypertension.