Adenylate cyclase activation is not sufficient to stimulate somatostatin release from dispersed cerebral cortical and diencephalic cells in glia-free cultures.
Under conditions in which vasoactive intestinal peptide (VIP) induces somatostatin release from cortical and diencephalic neuronal cultures, VIP causes large increases in intracellular cyclic AMP. Both the release of somatostatin and the increase in cyclic AMP elicited by VIP require exogenous calcium, can be blocked by cobalt ion, and can be qualitatively mimicked by depolarizating concentrations of exogenous potassium ion. Direct activation of adenylate cyclase by forskolin causes large increases in cyclic AMP content but does not induce somatostatin release. In the absence of VIP, the calcium ionophore, ionomycin, and the phorbol ester, phorbol 12-myristate-13-acetate, also stimulate somatostatin release. These results indicate that VIP-stimulation of cyclic AMP formation and VIP-stimulation of somatostatin release are calcium-dependent and that the two phenomena are dissociatable. Cyclic AMP formation is not a necessary condition for VIP-induced somatostatin release. Nucleotide formation may be a sufficient condition for release or, possibly in association with calcium influx, it may be an event unrelated to the release process.
Tapia-Arancibia
L
L
Unité de Neurobiologie endocrinologique, C.N.R.S. UA 1197, Université de Montpellier II, France.
Pares-Herbute
N
N
Astier
H
H
Reichlin
S
S
Nathanson
J
J
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D003561:Cytarabine; D004027:Diencephalon / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007150:Immunohistochemistry; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D013004:Somatostatin / Q000378:metabolism*; D013997:Time Factors; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*
D003561:Cytarabine; D005576:Colforsin; D014660:Vasoactive Intestinal Peptide; D013004:Somatostatin; D000262:Adenylyl Cyclases; D002118:Calcium; D015056:1-Methyl-3-isobutylxanthine