Effect of dl-demethylcoclaurine on cultured rat heart cells

Cells from newborn rat hearts were cultured in Eagle MEM. Chronotropican inotropic responses of the cells to dl-demethylcoclaurine (DMG) were recorded photoelectrically. The rate of contractions of the cells increased significantly when DMG was added. At the final concentration of 10(-6), 10(-5), 10(-4), and 10(-3) M, the beating rate increased by 19, 32, 26, and 18%, respectively. At 10(-5) and 10(-4) M the amplitudes of beats of the contractions of some cell clusters, but decreased in others. Both the rate and amplitude of contractions were augmented significantly in 10(-6) M isoprenaline (ISO). The positive chronotropic and inotropic responses to ISO were greater than those elicited by DMC. Anti-arrhythmic effect was seen in ISO 10(-6) M or DMC 10(-5)-10(-4) M. The effects of both ISO 10(-6) M and DMC 10(-5) M were antagonized by pindolol (PIN) 10(-6)-10(-5) M. However, PIN per se did not alter the beating rate. The results indicate that DMC activate the beta adrenoreceptors of rat heart cells.