Cates J A, Abedin M Z, Saunders-Kirkwood K D, Moser A J, Giurgiu D I, Roslyn J J
Department of Surgery, University of California, School of Medicine, Los Angeles.
Surgery. 1995 Feb;117(2):206-12. doi: 10.1016/s0039-6060(05)80087-x.
Gallstone formation is characterized by increased biliary calcium (Ca2+) level and altered gallbladder absorption. Recent studies suggest that luminal Ca2+ regulates gallbladder ion transport via intracellular calcium ([Ca2+]ic). Ca2+-calmodulin and protein kinase C (PKC) are two major systems through which [Ca2+]ic carries out second-messenger functions in many cell types. We have previously shown that Ca2+-calmodulin regulates basal gallbladder ion transport in prairie dog. The present study tests the hypothesis that PKC is also essential in regulation of gallbladder ion transport in this model.
The role of PKC in regulation of gallbladder ion transport was determined by studying the effects of phorbol esters, synthetic analogues of diacylglycerol, which directly activates PKC. Gallbladders were mounted in Ussing chambers, and standard electrophysiologic parameters were recorded after exposing tissues to either 10(-5) mol/L of 4-alpha-phorbol 12,13-didecanoate (PDD), 4-beta-phorbol 12-myristate 13-acetate, 4-beta-phorbol 12,13-dibutyrate (PDB), or 10(-4) mol/L serotonin. Unidirectional Na+, Cl-, and H2O fluxes were measured before and after treatment with only inactive PDD and most active PDB.
Mucosal and serosal exposure of tissues to either 4-beta-phorbol 12-myristate 13-acetate or PDB resulted in a decrease in short-circuit current and transepithelial potential difference without any change in tissue resistance. Serotonin induced similar changes in gallbladder electrical properties. PDB caused an inhibition of mucosal to serosal fluxes of Na+, Cl-, and H2O, with a decrease in net Na+ absorption, an increase in net Cl- secretion, and a conversion of net H2O absorption to net H2O secretion. Serosal-to-mucosal fluxes of Na+, Cl-, and H2O did not change. Inactive PDD had no effect on either electrophysiologic parameters or ion and water fluxes. Pretreatment of tissues with PKC antagonist 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine blocked the phorbol ester-induced inhibition of ion transport.
PKC regulates gallbladder ion transport in the prairie dog by inhibiting Na+ absorption and stimulating Cl- secretion.
胆结石形成的特征是胆汁钙（Ca2+）水平升高和胆囊吸收改变。最近的研究表明，管腔内Ca2+通过细胞内钙（[Ca2+]ic）调节胆囊离子转运。Ca2+-钙调蛋白和蛋白激酶C（PKC）是[Ca2+]ic在许多细胞类型中发挥第二信使功能的两个主要系统。我们之前已经表明，Ca2+-钙调蛋白调节草原犬鼠的基础胆囊离子转运。本研究检验了PKC在该模型中对胆囊离子转运调节也至关重要这一假设。
通过研究佛波酯（二酰基甘油的合成类似物，可直接激活PKC）的作用来确定PKC在调节胆囊离子转运中的作用。将胆囊安装在尤斯灌流小室中，在将组织暴露于10(-5)mol/L的4-α-佛波醇12,13-二癸酸酯（PDD）、4-β-佛波醇12-肉豆蔻酸酯13-乙酸酯、4-β-佛波醇12,13-二丁酸酯（PDB）或10(-4)mol/L血清素后，记录标准电生理参数。在用无活性的PDD和活性最强的PDB处理前后，测量单向Na+、Cl-和H2O通量。
将组织黏膜和浆膜暴露于4-β-佛波醇12-肉豆蔻酸酯13-乙酸酯或PDB均导致短路电流和跨上皮电位差降低，而组织电阻无任何变化。血清素引起胆囊电特性类似的变化。PDB导致Na+、Cl-和H2O从黏膜到浆膜的通量受到抑制，净Na+吸收减少，净Cl-分泌增加，净H2O吸收转变为净H2O分泌。Na+、Cl-和H2O从浆膜到黏膜的通量未改变。无活性的PDD对电生理参数或离子及水通量均无影响。用PKC拮抗剂1-(5-异喹啉磺酰基)-2-甲基哌嗪预处理组织可阻断佛波酯诱导的离子转运抑制。
PKC通过抑制Na+吸收和刺激Cl-分泌来调节草原犬鼠的胆囊离子转运。
