Pharmacology of the adrenoceptors and cholinoceptors of the BC3H1 nonfusing muscle cell line.

1. We have studied the action of different transmitters on the transmembrane 42K or 86Rb efflux from tissue cultures of the BC3H1 muscle cell line. 2. The effect of catecholamines and carbachol (CCh) on the isotope efflux rate was measured by addition of the drugs at different times during the washout. 3. Noradrenaline (NA), phenylephrine (Phe), isoprenaline (Iso) and CCh increased 42K and 86Rb efflux rate in a dose-dependent manner. 4. The action of NA seems to be due exclusively to the stimulation of alpha-receptors, since its effect was blocked by phentolamine but not by propranolol. The effects of Iso on the 86Rb efflux were inhibited by propranolol. The beta-receptors in the BC3H1 cells seem to be the beta2-type since they are stimulated by Iso and insensitive to NA. 5. The effect of CCh was blocked (+)-tubocurarine but not by atropine. This result confirms the presence of nicotinic receptors in BC3H1 cells.