Transmitter-like action of ATP on patched membranes of cultured myoblasts and myotubes

Abstract

The concept of purinergic neurotransmission, first proposed by Burnstock1, has been confirmed in various cell types. We show here, by the patch-clamp method2, that external ATP in micromotor concentrations (1–100 µM) activates cation channels in the membranes of fusion-competent myoblasts and myotubes. In cell-attached membrane patches of myoblasts and myotubes the mean number of simultaneously activated channels increases with time after external ATP application. In myoblasts only one population of channels having a mean single-channel conductance of γ=43 pS was found, while in myotubes two populations with γ1=48 pS and γ2 = 20 pS were observed. Treatment of myotube membranes with acetylcholine (ACh) or carbachol resulted in two populations of channels which had conductance values and voltage-dependent mean channel lifetimes similar to those produced in response to ATP. The results show that embryonic skeletal muscle cells contain cation channels sensitive to ATP and provide evidence for a neurotransmitter-like action of ATP on these cells.