Endothelin-1 (ET-1) has been shown to be a potent growth factor and to induce cardiac hypertrophy. In the present study, we examined the role of G protein, protein kinase C (PKC) and Na(+)-H+ exchanger in ET-1-induced cardiac hypertrophy in cultured neonatal rat cardiac myocytes. ET-1 (10(-10)-10(-7) mol/L) induced promotion of 3H-leucine incorporation, increase in cell protein content and cell surface area in a dose-dependent manner with EC50 value of 5.2 x 10(-10), 5.2 x 10(-10) and 7.3 x 10(-10) mol/L respectively. All of these ET-1-induced cardiomyocyte hypertrophic responses were completely blocked by pretreatment with staurosporine (2 nmol/L), a protein kinase C inhibitor, and stimulated by 4-phorbol, 12-myristate, 13-acetate (PMA) (10(-8)-10(-6) mol/L), a protein kinase C activator, in a dose-dependent manner. Pretreatment of amiloride (10(-4) mol/L), a Na(+)-H+ exchange inhibitor completely inhibited the ET-1-induced, but not PMA-induced cardiomyocyte hypertrophic responses. The ET-1-induced increase in cardiomyocyte protein synthesis and cell surface area was significantly inhibited by pretreatment with pertussis toxin (150 ng/ml). These results suggest that ET-1-induced cardiomyocyte hypertrophy was linked with pertussis toxin sensitive G protein, and PKC and Na(+)-H+ exchange may be an important intracellular signaling transduction pathway during ET-1-induced cardiac hypertrophy in cultured neonatal rat cardiac myocytes.