[Effects of praeruptorin C on spontaneous contraction and action potential in cultured myocardial cells of neonatal rats].

Using a circuit TV system and method of intracellular standard microelectrode, the effects of praeruptorin C on spontaneous contractile behavior and action potential were observed in cultured myocardial cells of neonatal rats. There was a decline in both the contractile frequency and velocity of cell edge motion after exposure to Pra-C for 5 minutes. Pra-C (10, 30 and 100 mumol.L-1) was shown to inhibit contraction velocity by 24%, 43% and 51%, respectively in a concentration dependent manner. Pra-C (30 and 100 mumol.L-1) inhibited the contractile frequency by 13% and 19%, respectively. Nifedipine 3 mumol.L-1 shortened APD50 and APD90 by 14% and 17% but verapamil at the same concentration inhibited APA by 27%, shortened APD50 by 8% and prolonged APD90 and SCL by 10% and 43%, respectively. Pra-C 10, 30 and 100 mumol.L-1 shortened the APD50 by 7%, 14% and 18%, respectively. Pra-C 30 mumol.L-1 inhibited APA and prolonged SCL. The results suggest that the effects of Pra-C on contractile behavior and action potential were related to its Ca2+ channel blockade.