EFFECTS OF PRAERUPIORIN 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 μmol·L^-1)was shown to inhibit contraction velocity by 24%,43%and 51%, respectively in a concentration dependent manner.Pra-c(30 and 100μmol·L^-1)inhibited the contractile frequency by 13%and 19%,respectively. Nifedipine 3 μmol·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 l0%and 43%, respectively. Pra-C10, 30 and 100μmol·L^-1 shortened the APD50 by 7%,14%and l8%, respectively. Pra-C 30μmol·L^-1 inhibited APA and prolonged SCL.The results suggest that the effects of Pra-C on cotractile behavior and action potential were related to its Ca²⁺ channel blockade.