Galanin increases cytoplasmic calcium in insulin-producing RINm5F cells by activating phospholipase C

We showed previously that the neuropeptide, galanin, transiently and promptly increases the cytoplasmic concentration of Ca2+, [Ca2+](i), in insulin producing clonal RINm5F cells prior to a reduction in [Ca-2+](i). In this study, we examined the mechanisms underlying the increased [Ca2+](i). We found that galanin (100 nM) transiently increased the [Ca2+](i) in the presence of 15 mM glyceraldehyde and 3.3 mM glucose. This effect was abolished by both the inhibitor of the microsomal Ca2+ ATPase, thapsigargin, which depletes the intracellular Ca2+ stores, and the specific inhibitor of phospholipase C, U73122. In contrast, the blocker of L-type Ca2+ release, ryanodine, did not affect galanin-induced increase in [Ca2+](i). Thus, galanin induces a rapid mobilization of Ca2+ from intracellular Ca2+ stores in insulin producing RINm5F cells by an effect mediated by activated phospholipase C. (C) 1996 Academic Press, Inc.