Calcitonin secretion and cyclic AMP-efflux from C-cells, stimulated by glucagon and either calcium or Bay K 8644.

The interaction of glucagon and either calcium or Bay K 8644 on calcitonin (CT)-release and cAMP-efflux was studied in a rat C-cell line, (rMTC 6-23). CT secretion was stimulated by glucagon up to 216%, ionized calcium (Ca++) up to 112%, and Bay K 8644 up to 81% above the control. The combination of glucagon with either Ca++ or Bay K 8644 resulted in an additive effect. cAMP-efflux was grossly incremented by glucagon (536 pmol/mg), slightly by Ca++ (11.6 pmol/mg) and not at all by Bay K 8644 (less than 3 pmol/mg). The combination of glucagon with either calcium or Bay K 8644 caused a reduction of the cAMP-increase obtained by glucagon alone. These data suggest complex interactions between the cAMP and the intracellular calcium-dependent pathway, but an additive effect of the two pathways on CT-release.