ENDOTHELIN-1 STIMULATES HYPERTROPHY AND CONTRACTILITY OF NEONATAL RAT CARDIAC MYOCYTES IN A SERUM-FREE MEDIUM .2.

The effect of endothelin-1 (ET-1) on rat cardiac myocytes cultured in a serum-free medium was determined. Cardiac myocytes cultured in our medium showed an increased rate of protein synthesis, morphological size, contraction rate, and Ca2+ uptake when ET-1 was added. These actions of ET-1 were inhibited by a protein kinase C inhibitor, H-7. Among these four phenomena, contraction and Ca2+ uptake were inhibited by a Ca2+ channel blocker, nicardipine. Therefore, it is likely that the signal for ET-1 to induce these phenomena is transduced by kinase C, and Ca2+ uptake is related to maintaining a high contraction rate.