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% beta-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 (5-40 microg/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 (15-300 microg/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 (0.1-3.0 microg/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 beta-alanine (3 g/kg; i.v., 30-minutes) did not alter angiotensin II-induced hemodynamic responses. Similarly, incubation of aortic rings with beta-alanine (40mM, 30 minutes) did not affect the contractile responses to angiotensin II. The results suggest that beta-alanine, per se, does not affect angiotensin II-induced responses in rat. However, beta-alanine-induced taurine depletion is associated with a reduction in the pressor response to angiotensin II without impairing baroreflex function.
Mozaffari
M S
MS
Department of Oral Biology and Maxillofacial Pathology, Medical College of Georgia, School of Dentistry, Augusta 30912-1128, USA.
Abebe
W
W
D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D017704:Baroreflex / Q000187:drug effects / Q000502:physiology; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate / Q000187:drug effects* / Q000502:physiology; D008297:Male; D009599:Nitroprusside / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D051381:Rats; D011921:Rats, Inbred WKY; D013654:Taurine / Q000494:pharmacology / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D009599:Nitroprusside; D013654:Taurine; D010656:Phenylephrine