Dibutyryl cyclic AMP effects on calcium metabolism by mouse mastocytoma cells

Abstract

The ability of mouse mastocytoma cells to take up 45Ca 2+ was measured in normal growth medium. As previously observed in physiological buffers with succinate and Pi, cells grown for 18h with N 6,O 2′-dibutyryladenosine 3′,5′ cyclic monophosphate (DB cyclic AMP) to inhibit growth took up more 45Ca 2+ than untreated cells. However 45Ca 2+ uptake by cells in growth medium was less sensitive to respiratory inhibitors or uncouplers than 45Ca 2+ uptake in physiological buffer. Increased 45Ca 2+ uptake by 18h cyclic nucleotide-treated cells was not a result of tighter mitochondrial coupling since mitochondria prepared from cyclic nucleotide-treated cells were less coupled than those from untreated cells. Nevertheless studies with uncouplers suggested that the bulk of the intracellular Ca 2+ was associated with mitochondria. DB cyclic AMP-treated cells contained less total Ca 2+ than untreated cells indicating that net Ca 2+ efflux occurred during the 18h period of drug treatment. These observations suggest that Ca 2+ fluxes increase in DB cyclic AMP-treated PY815 cells and that a net efflux of Ca 2+ occurs during growth inhibition by the cyclic nucleotide.