CHRONIC STIMULATION OF ACETYLCHOLINE-RECEPTORS - DIFFERENTIAL-EFFECTSON NA,K-ATPASE ISOFORMS IN A MYOGENIC CELL-LINE

The myogenic cell line, C2C12, expresses two isoforms of the Na,K-ATPa se catalytic subunit (alpha 1 and alpha 2) following differentiation. Hyperpolarization in myotubes following long-term exposure to carbacho l (Henning et al. (1993) Br. J. Pharmacol., 111:459-464) suggests that the activity of one or both of the isoforms is increased after chroni c stimulation of the acetylcholine receptor. We have examined explicit ly the abundance of the two isoforms following such an exposure. Immun oblotting with specific antibodies did not detect any changes in the a bundance of the alpha 1 isoform after a 3-day exposure to carbachol(10 mu M). In contrast, there was a 50% increase in the abundance of alph a 2. These results suggest that chronic stimulation of the acetylcholi ne receptor produced a differential effect on the abundance of the alp ha isoforms. (C) 1996 Wiley-Liss, Inc.