Traynor-Kaplan A E, Buranawuti T, Vajanaphanich M, Barrett K E
Department of Medicine, School of Medicine, University of California, San Diego 92103.
Am J Physiol. 1994 Nov;267(5 Pt 1):C1224-30. doi: 10.1152/ajpcell.1994.267.5.C1224.
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.
卡巴胆碱可诱导T84细胞分泌钙依赖性氯离子，并激活蛋白激酶C。然而，用卡巴胆碱长时间刺激或直接激活蛋白激酶C会抑制随后的钙依赖性氯离子分泌。此外，卡巴胆碱升高肌醇四磷酸水平的能力可能与氯离子分泌的抑制有关。在此我们证明，蛋白激酶C激活会增加T84结肠上皮细胞中肌醇四磷酸（1,3,4,6 - 和3,4,5,6 - 异构体）的水平。此外，这与氯离子分泌的抑制相对应。然而，蛋白激酶C不太可能介导卡巴胆碱的类似作用。星形孢菌素既不能逆转卡巴胆碱抑制钙依赖性氯离子分泌的能力，也不能逆转其对肌醇3,4,5,6 - 四磷酸水平的影响。与蛋白激酶C激活剂相比，卡巴胆碱对肌醇四磷酸异构体的影响在数量和质量上也有所不同。因此，蛋白激酶C活性可增加T84细胞内各种肌醇四磷酸异构体的水平，但不介导卡巴胆碱诱导的这些假定信使的增加。这些数据进一步支持了以下假设：肌醇3,4,5,6 - 四磷酸是一种负性第二信使，可使上皮细胞氯离子分泌与细胞内钙的变化解偶联。
