Taurine Regulation of Blood Pressure and Vasoactivity
Taurine plays an important role in the modulation of cardiovascular function by acting not only within the brain but also within peripheral tissues. We found that IV injection of taurine to male rats caused hypotension and tachycardia. A single injection of taurine significantly lowered the systolic, diastolic, and mean arterial blood pressure in freely moving Long–Evans control rats. We further confirm the vasoactive properties of taurine using isolated aortic ring preparations. Mechanical responses of circular aortic rings to pharmacological agents were measured by an isometric force transducer and amplifier. We found that bath application of taurine to the aortic rings caused vasodilation which was blocked by picrotoxin. Interestingly, picrotoxin alone induced a constriction of the aortic ring in the absence of exogenously added taurine, suggesting a tonic activation of GABAAreceptors by circulating either taurine or GABA. Additionally, we found that the endothelial cells express high levels of taurine transporters and GABAAreceptors. We have previously shown that taurine activates GABAAreceptors and thus we suggest that the functional implication of GABAAreceptor activation is the relaxation of the arterial muscularis, vasodilation, and a decrease in blood pressure. Interestingly however, the effects of acute taurine injection were very different than chronic supplementation of taurine. When rats were supplemented taurine (0.05%, 4 weeks) in their drinking water, taurine has significant hypertensive properties. The increase in blood pressure was observed however only in females; males supplemented with taurine did not show an increase in systolic, diastolic, or mean arterial pressure. In both genders however, taurine supplementation caused a significant tachycardia. Thus, we suggest that acute administration of taurine may be beneficial to lowering blood pressure. However, our data indicate that supplementation of taurine to females caused a significant increase in blood pressure. The effect of taurine supplementation on hypertensive rats remains to be seen.
Glutamic acid decarboxylase
- Abebe W, Mozaffari MS (2000) Effects of chronic taurine treatment on reactivity of the rat aorta. Aminosan 19:615–623Google Scholar
- El Idrissi A, Messing J, Scalia J, Trenkner E (2003) Prevention of Epileptic Seizures through taurine. In: Lombardini JB, Schaffer SW, Azuma J (eds) Taurine 5 Beginning the 21st Century, Adv Exp Med Biol, Vol 526, Kluwer Press, NewYork, pp 515–525Google Scholar
- Meldrum MJ, Tu R, Patterson T et al (1994) The effect of taurine on blood pressure, and urinary sodium, potassium and calcium excretion. In: Huxtable R, Michalk DV (eds) Taurine in health and disease. Plenum Press, New York, pp 207–215Google Scholar
- Nakagawa M, Takeda K, Yoshitomi T et al (1994) Antihypertensive effect of taurine on salt-induced hypertension. In: Huxtable R, Michalk DV (eds) Taurine in health and disease. Plenum Press, New York, pp 197–206Google Scholar
- Tsukada Y, Hirano S, Nagata Y, Mastutani T (1960) Metabolic studies of gamma-aminobutyric acid in mammalian tissues. In: Roberts E (ed) Inhibition in the nervous system and gamma-aminobutyric acid. Pergamon, New York, NY, p 163Google Scholar