Isomers of inositol trisphosphate in exocrine pancreas.
In rat pancreatic acinar cells, the Ca2+-mobilizing receptor-agonist, caerulein, at both maximal and submaximal concentrations, stimulated a rapid, transient, increase in [3H]inositol 1,4,5-trisphosphate [(1,4,5)IP3], followed by a slower, sustained, increase in [3H]inositol 1,3,4-trisphosphate [(1,3,4)IP3]. Neither activation of protein kinase C by phorbol dibutyrate nor prevention of the caerulein-stimulated elevation of cytosolic [Ca2+] significantly affected the pattern of formation of the two isomers of IP3. Although carbachol evoked an increase in cytosolic [Ca2+], it did not significantly stimulate [3H](1,4,5)IP3 accumulation, but did promote [3H](1,3,4)IP3 accumulation. Moreover, both carbachol and caerulein maintained hormone-sensitive intracellular Ca2+ pools in a Ca2+-depleted state after [3H](1,4,5)IP3 had returned to basal concentrations. One interpretation of these findings is that total cellular concentrations of [3H](1,4,5)IP3 may not accurately reflect the concentration of this putative mediator in biologically relevant compartments.
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D002108:Ceruletide / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000378:metabolism*; D007536:Isomerism; D008297:Male; D010179:Pancreas / Q000187:drug effects / Q000378:metabolism*; D015240:Phorbol 12,13-Dibutyrate; D010703:Phorbol Esters / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013403:Sugar Phosphates / Q000378:metabolism*
D007295:Inositol Phosphates; D010703:Phorbol Esters; D013403:Sugar Phosphates; D015240:Phorbol 12,13-Dibutyrate; D015544:Inositol 1,4,5-Trisphosphate; D002108:Ceruletide; D002217:Carbachol; D002118:Calcium