title: Histamine-stimulated phospholipase C signalling in the adrenal chromaffin cell: effects on inositol phospholipid metabolism and tyrosine hydroxylase phosphorylation.
abstract: 1. The present report gives a detailed account of histamine-stimulated phospholipase C (PLC) activity in bovine adrenal chromaffin cells. 2. Histamine activation of H1 receptors stimulates PLC with a biphasic sensitivity to extracellular Ca2+. The initial response (the first 15 s stimulation) was not reduced by the removal of extracellular Ca2+, whereas the maintenance of PLC activity beyond this time required Ca2+ influx. 3. Phospholipase C activity in response to a 10 min incubation with histamine was inhibited by La3+ (3 mmol/L) or SKF96365 (10 mumol/L). Nifedipine (10 mumol/L), but not omega-agatoxin IVA (100 nmol/L) or omega-conotoxin GVIA (300 nmol/L), produced a partial inhibition of PLC activity. The response was also partially inhibited by a reduction in the extracellular Cl- concentration (40 mmol/L) or by the inclusion of the Cl- channel blocker N-phenylanthranilic acid (300 mumol/L). 4. Kinetic analysis of the rate of turnover of the various inositol phosphate isomers in response to histamine suggested that the inositol monophosphates were being produced from a source in addition to inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) metabolism. This conclusion was supported by the differential action of pertussis toxin and neomycin on Ins(1,4,5)P3 formation compared with inositol monophosphate formation. 5. We have attempted to identify a defined role for the intracellular Ca2+ mobilized in these cells in response to histamine. After short incubations (up to 3 min), histamine was able to regulate the site-specific phosphorylation of tyrosine hydroxylase, the rate-limiting enzyme in catecholamine synthesis. This observation has important implications for a possible role for the PLC signalling pathway in controlling the rate of catecholamine biosynthesis.
authors.affiliation: Neuroscience Group, Faculty of Medicine and Health Sciences, University of Newcastle, Callaghan, New South Wales, Australia. bcsjb@medicine.newcastle.edu.au
authors.forename: S J
authors.initials: SJ
authors.lastname: Bunn
authors.forename: P R
authors.initials: PR
authors.lastname: Dunkley
mesh_terms: D000313:Adrenal Medulla / Q000187:drug effects*; D000818:Animals; D002417:Cattle; D019439:Chromaffin Cells / Q000187:drug effects*; D006632:Histamine / Q000494:pharmacology*; D010716:Phosphatidylinositols / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010738:Type C Phospholipases / Q000187:drug effects*; D014446:Tyrosine 3-Monooxygenase / Q000187:drug effects*
chemical_list: D010716:Phosphatidylinositols; D006632:Histamine; D014446:Tyrosine 3-Monooxygenase; D010738:Type C Phospholipases