Increase in cytosolic Ca2+ induced by elevation of extracellular Ca2+ in skeletal myogenic cells

Abstract

Cytoplasmic Ca2+concentration ([Ca2+]i) variation is a key event in myoblast differentiation, but the mechanism by which it occurs is still debated. Here we show that increases of extracellular Ca2+ concentration ([Ca2+]o) produced membrane hyperpolarization and a concentration-dependent increase of [Ca2+]i due to Ca2+influx across the plasma membrane. Responses were not related to inositol phosphate turnover and Ca2+-sensing receptor. [Ca2+]o-induced [Ca2+]i increase was inhibited by Ca2+ channel inhibitors and appeared to be modulated by several kinase activities. [Ca2+]i increase was potentiated by depletion of intracellular Ca2+ stores and depressed by inactivation of the Na+/Ca2+exchanger. The response to arginine vasopressin (AVP), which induces inositol 1,4,5-trisphosphate-dependent [Ca2+]i increase in L6-C5 cells, was not modified by high [Ca2+]o. On the contrary, AVP potentiated the [Ca2+]i increase in the presence of elevated [Ca2+]o. Other clones of the L6 line as well as the rhabdomyosarcoma RD cell line and the satellite cell-derived C2-C12 line expressed similar responses to high [Ca2+]o, and the amplitude of the responses was correlated with the myogenic potential of the cells.