Cardiovascular responses of the taurine-depleted rat to vasoactive agents

The objective of this study was to assess the effect of taurine-depletion on cardiovascular responses of rat to vasoactive agents. Male Wistar-Kyoto (WKY) rats were given either tap water (control) or 3% β-alanine (taurine-depleted) for three weeks. Thereafter, mean arterial pressure (MAP) and heart rate of the freely moving animal were measured in response to vasoactive agents. Administration of phenylephine (5-40μg/kg/min; i.v.) resulted in a similar and significant increase in MAP but a reduction in heart rate in both control and taurine-depleted groups. On the other hand, administration of sodium nitroprusside (15-300μg/kg/min; i.v.) elicited a similar and significant reduction in MAP but increased heart rate in both groups. Lack of a differential response to phenylephrine and sodium nitroprusside between the two groups suggests that baroreflex regulation of cardiovascular function is not adversely affected by taurine-depletion. Administration of angiotensin II (0.1-3.0μg/kg/min; i.v.) resulted in a dose-related increase in the pressor response and a decrease in heart rate in both groups. However, angiotensin II-induced pressor response was reduced in the taurine-depleted compared to the control rats (p < 0.05); heart rate was similarly reduced in both groups. Acute exposure to β-alanine (3g/kg; i.v., 30-minutes) did not alter angiotensin II-induced hemodynamic responses. Similarly, incubation of aortic rings with β-alanine (40mM, 30 minutes) did not affect the contractile responses to angiotensin II. The results suggest that β-alanine, per se, does not affect angiotensin H-induced responses in rat. However, β-alanine-induced taurine depletion is associated with a reduction in the pressor response to angiotensin II without impairing baroreflex function.