Effect of taurine on angiotensin II-induced expression of immediate early response genes in primary cultured neonatal rat heart cells

Taurine-deficient dilated cardiomyopathy in a family of golden retrievers

A reversible taurine-deficient dilated cardiomyopathy occurred in five related golden retrievers. An apical systolic heart murmur was the most common physical abnormality. According to fractional shortening and end-systolic diameter on echocardiography, significant improvements (P<0.005) were recorded within 3 to 6 months of starting taurine supplementation. The dogs regained substantial systolic function, and four were weaned off all cardiac medications except taurine. This response to therapy was unusual, because canine dilated cardiomyopathy is generally progressive and fatal.

Taurine improves angiotensin II-induced hypertrophy of cultured neonatal rat heart cells

The effect of taurine on angiotensin II-induced hypertrophy of cultured neonatal rat heart cells (myocytes and nonmyocytes) was examined. Angiotensin II (1-100 nM) alone caused an increase in the rate of protein synthesis and the surface area of myocytes without altering the rate of DNA synthesis or cell number. It also mediated an increase in DNA synthesis and in cell number of nonmyocytes. Exposure of the cells to taurine (20 mM) in the absence of angiotensin II had no effect on either hyperplastic growth or hypertrophy of the two types of cultured cardiac cells. However, myocytes pretreated with 20 mM taurine exhibited reduced responsiveness to angiotensin II. Following a 24 hr pretreatment with 20 mM taurine, the stimulation in protein synthesis by angiotensin II (1 nM) was significantly suppressed. Similarly, taurine treatment of nonmyocytes reduced the degree of angiotensin II-induced promotion of hyperplastic growth (DNA synthesis and cell number). Finally, taurine partially prevented the rise in [Ca2+]i mediated by angiotensin II in cardiac cells. The present results indicate that taurine is an effective inhibitor of angiotensin II action. The possibility that the beneficial effects of taurine in the treatment of heart failure might be related to its suppression of angiotensin II-mediated cellular responses is discussed.

Effects of taurine on signal transduction steps induced during hypertrophy of rat heart myocytes

Angiotensin II plays an important role in the development of cardiac hypertrophy. One factor thought to contribute to the trophic activity of angiotensin II in fibroblasts is the elevation in [Ca2+]i. Although this theory has received considerable support in cardiac fibroblasts, it is much more controversial in cardiac myocytes. Therefore, the aim of this report was to examine the effect of several Ca2+ modulators on protein synthesis in neonatal cardiac myocytes. We found that angiotensin II increased both [Ca2+]i and the rate of protein synthesis in isolated myocytes. Both effects were blocked by nifedipine, but only the angiotensin II-mediated increase in [Ca2+]i was inhibited by taurine in a dose-dependent manner. These data support the notion that Ca2+ plays only a permissive role in angiotensin II-mediated stimulation of protein synthesis. By contrast, the ability of taurine to attenuate the positive chronotropic effect, the prolongation of the action potential and the proarrhythmic activity of angiotensin II appear to be linked directly to changes in [Ca2+]i. We conclude that taurine reverses these actions of angiotensin II by altering Ca2+ flux across the cell membrane.