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.