BETA-ADRENERGIC RECEPTORS AND MYOGENESIS

Abstract

The rat myogenic cell line, L8, contains a .beta.-adrenergic catecholamine-sensitive adenylate cyclase. Prior to cell fusion, and continuing thereafter, .beta.-adrenergic sites, as determined by the stereospecific binding of (125I)-hydroxybenzylpindolol, [(125I)IHYP] increases from 470 to 2000 sites/cell. There is also an increase in adenylate cyclase (2-to 5-fold) and endogenous c[cyclic]AMP (5- to 30-fold) following stimulation by catecholamine. The dissociation constant (KD) of (125I)IHYP for unfused and fused cell-homogenates, as determined by estimation with Scatchard analysis, by direct determination at receptor concentrations well below the KD, or by association (4.6 .times. 108 M-1 min-1), and dissociation (0.028 min-1) kinetics, ranged from about 40-70 pM. The acquisition of .beta.-receptors prior to fusion in L8 cells may implicate this system in the regulation of myogenesis.