Elevated intracellular Ca2+ acts through protein kinase C to regulate rabbit ileal NaCl absorption. Evidence for sequential control by Ca2+/calmodulin and protein kinase C.
Calcium/calmodulin is involved in the regulation of basal rabbit ileal active Na and Cl absorption, but the mechanism by which elevated intracellular Ca2+ affects Na and Cl transport is unknown. To investigate the roles of the Ca2+/calmodulin and protein kinase C systems in ileal NaCl transport, two drugs, the isoquinolenesulfonamide, H-7, and the naphthalenesulfonamide, W13, were used in concentrations that conferred specificity in the antagonism of protein kinase C (60 microM H-7) and Ca2+/calmodulin (45 microM W13), respectively, as determined using phosphorylation assays in ileal villus cells. W13 but not H-7 stimulated basal active NaCl absorption. H-7 inhibited changes in Na and Cl absorption caused by maximal concentrations of Ca2+ ionophore A23187 and carbachol and serotonin, secretagogues that act by increasing cytosol Ca2+, while W13 had no effect. In contrast, neither H-7 nor W13 altered the change in NaCl transport caused by the cyclic nucleotides 8-Br-cAMP and 8-Br-cGMP. These data suggest that: (a) basal rabbit ileal NaCl absorption is regulated by the Ca2+/calmodulin complex and not by protein kinase C; (b) the effect of elevating intracellular Ca2+ to decrease NaCl absorption is mediated via protein kinase C but not by Ca2+/calmodulin; (c) the effects of protein kinase C are not overlapping or synergistic with those of Ca2+/calmodulin on either basal absorption or on the effects of increased Ca2+; and (d) neither Ca2+/calmodulin nor protein kinase C are involved in the effects of cAMP and cGMP on ileal active NaCl transport.
Donowitz
M
M
Department of Medicine, Tufts University School of Medicine, Boston, Massachusetts.
Cohen
M E
ME
Gould
M
M
Sharp
G W
GW
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000818:Animals; D001095:Arachidonic Acids / Q000378:metabolism; D001693:Biological Transport, Active / Q000187:drug effects; D001826:Body Fluids / Q000201:enzymology*; D002118:Calcium / Q000502:physiology*; D002147:Calmodulin / Q000037:antagonists & inhibitors / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000201:enzymology; D004573:Electrolytes / Q000378:metabolism; D007082:Ileum; D007408:Intestinal Absorption; D007424:Intracellular Fluid / Q000201:enzymology* / Q000378:metabolism / Q000502:physiology; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D008871:Microvilli / Q000201:enzymology / Q000502:physiology; D009712:Nucleotides, Cyclic / Q000502:physiology; D010766:Phosphorylation; D010879:Piperazines / Q000494:pharmacology; D011451:Prostaglandin-Endoperoxide Synthases / Q000502:physiology; D011493:Protein Kinase C / Q000378:metabolism / Q000502:physiology*; D011817:Rabbits; D012965:Sodium Chloride / Q000502:physiology*; D013449:Sulfonamides / Q000494:pharmacology
D001095:Arachidonic Acids; D002147:Calmodulin; D004573:Electrolytes; D007546:Isoquinolines; D009712:Nucleotides, Cyclic; D010879:Piperazines; D013449:Sulfonamides; D012965:Sodium Chloride; C033772:N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011451:Prostaglandin-Endoperoxide Synthases; D011493:Protein Kinase C; D002118:Calcium