Protein kinase C activity does not mediate the inhibitory effect of carbachol on chloride secretion by T84 cells.
Carbachol induces calcium-dependent chloride secretion and activates protein kinase C in T84 cells. However, prolonged stimulation with carbachol or direct activation of protein kinase C inhibits subsequent calcium-dependent chloride secretion. Furthermore, the ability of carbachol to elevate inositol tetrakisphosphate levels may be linked to inhibition of chloride secretion. Here we demonstrate that protein kinase C activation increases levels of inositol tetrakisphosphates (1,3,4,6- and 3,4,5,6-isomers) in T84 colonic epithelia. Furthermore, this corresponds to an inhibition of chloride secretion. However, protein kinase C is unlikely to mediate the analogous effects of carbachol. Neither the ability of carbachol to inhibit calcium-dependent chloride secretion nor its effects on inositol 3,4,5,6-tetrakisphosphate levels were reversed by staurosporine. Carbachol also has quantitatively and qualitatively different effects on inositol tetrakisphosphate isomers than protein kinase C activators. Thus protein kinase C activity can increase levels of various inositol tetrakisphosphate isomers within T84 cells but does not mediate carbachol-induced increases in these putative messengers. These data further support the hypothesis that inositol 3,4,5,6-tetrakisphosphate is a negative second messenger, uncoupling epithelial chloride secretion from changes in intracellular calcium.
Department of Medicine, School of Medicine, University of California, San Diego 92103.
A E
AE
Traynor-Kaplan
T
T
Buranawuti
M
M
Vajanaphanich
K E
KE
Barrett
D000470:Alkaloids / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002217:Carbachol / Q000494:pharmacology*; D002460:Cell Line; D002712:Chlorides / Q000037:antagonists & inhibitors* / Q000378:metabolism; D003106:Colon / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007295:Inositol Phosphates / Q000378:metabolism; D007413:Intestinal Mucosa / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000470:Alkaloids; D002712:Chlorides; D007295:Inositol Phosphates; C081652:inositol-3,4,5,6-tetrakisphosphate; D002217:Carbachol; D011493:Protein Kinase C; D019311:Staurosporine; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium