GLUCAGON-INDUCED CA2+ MOVEMENT

We recently demonstrated that although glucagon increases the cytoplas mic free calcium concentration at all doses as vasoactive agents, ther e was a difference between high and low concentrations of glucagon. Th at is, extracellular calcium influences glucagon-induced calcium movem ent at a high concentration and extracellular calcium does not influen ce glucagon-induced calcium movement at a low concentration. In the pr esent study, in addition to previous data, we demonstrated that at a l ow concentration glucagon did not produce cAMP but produced inositol t risphosphate and that the increase in [Ca2+](c) was not affected by ex tracellular calcium. In contrast, at a high concentration, glucagon di d not promote inositol trisphosphate production but enhanced cAMP form ation and increased [Ca2+](c), which was affected by extracellular cal cium.