Second messenger function of inositol 1,4,5-trisphosphate. Early changes in inositol phosphates, cytosolic Ca2+, and insulin release in carbamylcholine-stimulated RINm5F cells.

摘要: The second messenger function of inositol 1,4,5-trisphosphate (Ins-1,4,5-P3) was investigated in carbamylcholine-stimulated RINm5F cells by analysis the early changes phosphates, cytosolic free Ca2+ concentration ([Ca2+]i), and insulin secretion. After a lag 2 s, [Ca2+]i rose to peak at 13 +/- response which due mainly mobilization from intracellular stores since it persisted even absence extracellular Ca2+. had already declined toward prestimulatory levels time secretion reached its maximal rate (2-3 min). Although rises trisphosphate preceded those both bisphosphate monophosphate, all three attained concentrations after 1 min remained elevated for least 10 min. accumulation truly Ca2+-independent under conditions rise abolished prior depletion pools. Further high performance liquid chromatography revealed presence two isomers, Ins-1,4,5-P3 Ins-1,3,4-P3 stimulated cells. latter virtually absent nonstimulatory but started accumulate 5-s 30 s stimulation. doubled within carbamylcholine addition, 5 and, although declining thereafter, slightly 3 Hence, onset that [Ca2+]i, turn release. These results strongly suggest acts as mobilizes during initiation