Endothelin-1 (ET-1) is involved in the development of cardiac hypertrophy and heart failure. We investigated the effects of ET-1 on intracellular calcium transient and its mechanisms. Neonatal rat cardiomyocytes were prepared and calcium transient was measured using fura-2. Treatment with ET-1 for 48 h prolonged calcium transient decay. In the presence of thapsigargin, ET-1 did not alter calcium transient decay. On the other hand, the prolonged calcium transient decay was maintained even when sodium was removed from the bath solution. These results indicate that ET-1-induced prolongation of calcium transient decay is mainly due to the suppression of calcium uptake by sarcoplasmic reticulum, but not inhibition of the sodium/calcium exchanger. Northern blotting analysis revealed that sarcoplasmic reticulum ATPase (SERCA2) mRNA was decreased in ET-1-treated cardiomyocytes, and that this decrease was inhibited by BQ-123 but not by BQ-788. Moreover, pretreatment with chelerythrine partially restored the ET-1-induced decrease in SERCA2 mRNA, whereas phorbol 12-myristate 13-acetate markedly reduced SERCA2 gene expression. Real-time RT-PCR analysis showed abundant ETA receptor gene expression in cardiomyocytes. ET-1 reduces SERCA2 gene expression through the ETA receptor and PKC pathway, and prolongs intracellular calcium transient decay. Specific inhibition of the ETA receptor may be a possible therapeutic strategy for improving cardiac performance.