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 of myocytes without changing the rate of DNA synthesis and cell number. It mediated increases in DNA synthesis and cell number in nonmyocytes. Furthermore, at the lower concentration of 1 nM, it induced c-fos and c-jun expression in both cultured myocytes and nonmyocytes. Exposure of the cells to taurine (20 mM) in the absence of angiotensin II had no effect on either hyperplastic growth or immediate early response gene expression by the two types of cultured cardiac cells. However, myocytes pretreated for 24 h with 20 mM taurine exhibited reduced responsiveness to angiotensin II (1 nM), resulting in lower levels of angiotensin II-mediated stimulation in protein synthesis, and immediate early response gene expression was attenuated. Similarly, taurine treatment of nonmyocytes reduced the degree of hyperplastic growth (DNA synthesis and cell number) and immediate early response gene expression stimulated by angiotensin II. Finally, taurine partially prevented the increase in intracellular free calcium [Ca2+]i mediated by angiotensin II in cardiac cells. Our results indicate that taurine is an effective inhibitor of angiotensin II action.