Effects of a phorbol ester and isoquinoline sulfonamides on rabbit parietal cell function.
The role of protein kinase C (PKC) on gastric H+ secretion, as measured by aminopyrine (AP) uptake and other intracellular signal transduction products, was investigated in isolated rabbit parietal cells using the PKC activator 12-0-tetradecanoyl phorbol 13-acetate (TPA) and several PKC inhibitors, including isoquinoline sulfonamides (H-7, H-8, H-89 and HA-1004) and calphostin-C. TPA dose-dependently inhibited histamine (10(-4) M)- and carbachol (10(-4) M)-stimulated AP uptake without affecting the response to dibutyryl cyclic AMP (10(-3) M). H-7 and calphostin-C dose-dependently augmented secretagogue-stimulated AP uptake, whereas H-8 and H-89 inhibited the response to secretagogues, and HA-1004 had no effect. H-7 and calphostin-C-induced augmentation of AP uptake was blocked by a calcium (Ca++) antagonist, lanthanum chloride, which suggests that the enhanced AP response was regulated by extracellular Ca++. Moreover, H-7 treatment partially reversed the TPA (10(-7) M)-induced inhibition of secretagogue-stimulated AP uptake. TPA reduced histamine- and carbachol-stimulated cAMP and inositol 1,4,5-triphosphate production by 50% and 96%, respectively, with a concomitant reduction of adenylate cyclase and intracellular free Ca++ by 44% and 78%. TPA increased the distribution of membrane-associated PKC by 20% and decreased histamine-stimulated PKA by 30%. In contrast, H-7 inhibited both PKC and protein tyrosine kinase activity in vitro but had no effect on these parameters in vivo. The results indicate that TPA-induced inhibition of secretagogue-stimulated AP uptake in PC is presumably mediated by activation of PKC.
Nandi
J
J
Department of Medicine, SUNY Health Science Center, USA.
Bosche
M C
MC
Levine
R A
RA
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine / Q000494:pharmacology*; D000262:Adenylyl Cyclases / Q000378:metabolism; D000632:Aminopyrine / Q000493:pharmacokinetics; D000818:Animals; D002118:Calcium / Q000378:metabolism; D000242:Cyclic AMP / Q000096:biosynthesis; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D066298:In Vitro Techniques; D010295:Parietal Cells, Gastric / Q000187:drug effects* / Q000378:metabolism; D011493:Protein Kinase C / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011817:Rabbits; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D000632:Aminopyrine; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000242:Cyclic AMP; D011505:Protein-Tyrosine Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D000262:Adenylyl Cyclases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium