Epidermal growth factor inhibits carbachol-stimulated canine parietal cell function via protein kinase C.
OBJECTIVE
Epidermal growth factor (EGF) inhibits secretagogue-stimulated gastric acid secretion via an EGF receptor located on parietal cells. The aim of this study was to examine whether this growth factor inhibited carbachol-stimulated acid secretion through a protein kinase C-dependent mechanism.


METHODS
The effect of EGF on carbachol-stimulated aminopyrine uptake, inositol trisphosphate formation, and intracellular Ca2+ ([Ca2+]i) in purified cultured parietal cells was studied. The ability of protein kinase A and C inhibitors to alter the inhibitory action of EGF was assessed. EGF-mediated translocation and activation of protein kinase C in parietal cells were determined.


RESULTS
EGF dose dependently inhibited carbachol-stimulated aminopyrine uptake in a pertussis toxin-insensitive, genistein (tyrosine kinase inhibitor)--sensitive manner, with a maximal inhibitory effect (37.5% +/- 6.8%) achieved at 10(-7) mol/L. EGF did not significantly inhibit carbachol-stimulated inositol trisphosphate formation and did not alter the initial transient increase or sustained plateau in [Ca2+]i stimulated by this secretagogue. The protein kinase C inhibitors H-7 and staurosporine dose dependently reversed the inhibitory action of EGF, whereas H-89 (protein kinase A inhibitor) failed to alter the effect of EGF. EGF pretreatment increased the translocation of alpha and beta 1 isoforms of protein kinase C and stimulated kinase activity in parietal cells. EGF did not down-regulate the parietal cell muscarinic receptor.


CONCLUSIONS
The inhibitory action of EGF on carbachol-stimulated parietal cell activity seems to involve protein kinase C.
Wang
L
L
Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor, USA.
Wilson
E J
EJ
Osburn
J
J
DelValle
J
J
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000470:Alkaloids / Q000494:pharmacology; D000632:Aminopyrine / Q000493:pharmacokinetics; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology*; D002478:Cells, Cultured; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004285:Dogs; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005744:Gastric Acid / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007546:Isoquinolines / Q000494:pharmacology; D010277:Parasympathomimetics / Q000494:pharmacology*; D010295:Parietal Cells, Gastric / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D010879:Piperazines / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000378:metabolism; D019311:Staurosporine; D013449:Sulfonamides
D000470:Alkaloids; D004791:Enzyme Inhibitors; D007546:Isoquinolines; D010277:Parasympathomimetics; D010879:Piperazines; D011976:Receptors, Muscarinic; D013449:Sulfonamides; D000632:Aminopyrine; D004815:Epidermal Growth Factor; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D015544:Inositol 1,4,5-Trisphosphate; D002217:Carbachol; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D019311:Staurosporine; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D002118:Calcium