Lesage Gene D, Marucci Luca, Alvaro Domenico, Glaser Shannon S, Benedetti Antonio, Marzioni Marco, Patel Tushar, Francis Heather, Phinizy Jo Lynne, Alpini Gianfranco
Department of Internal Medicine, Scott & White Hospital and The Texas A&M University System HSC COM, Temple, TX, USA.
Hepatology. 2002 Sep;36(3):641-51. doi: 10.1053/jhep.2002.35537.
Insulin stimulates canalicular bile flow by interaction with hepatocytes. Insulin regulates the function of a number of epithelia through activation and membrane translocation of Ca(2+)-dependent PKC isoforms. No information exists regarding insulin regulation of ductal bile secretion. The aim of the study was to determine the role and mechanisms of action of insulin in the regulation of cholangiocyte secretion in BDL rats. We determined the subcellular localization of insulin receptor in cholangiocytes. We measured the effect of insulin on (1) secretin-stimulated cAMP levels in cholangiocytes and duct expansion in intrahepatic bile duct units (IBDUs) in the absence or presence of BAPTA/AM, H7 or rottlerin and (2) bile flow. We evaluated (1) if insulin effects are associated with activation of PKC alpha and (2) if activation of PKC causes inhibition of secretin-stimulated cAMP levels and PKA activity. We found insulin receptors only in the apical domain of cholangiocytes. Insulin inhibited secretin-induced choleresis and secretin-stimulated cholangiocyte cAMP levels. Insulin inhibited secretin-induced secretion in IBDUs when applied at the basolateral membrane or microinjected into IBDU lumen. Insulin inhibitory effects on cholangiocyte secretion were blocked by BAPTA/AM and H7. Insulin induced activation of PKC alpha, which decreased secretin-stimulated cAMP and PKA activity. In conclusion, insulin inhibited secretin-induced ductal secretion of BDL rats through activation of PKC and inhibition of secretin-stimulated cAMP and PKA activity. In conclusion, insulin counter-regulates cholangiocyte secretory processes in the BDL model, which is characterized by cholangiocyte proliferation.
胰岛素通过与肝细胞相互作用刺激胆小管胆汁流动。胰岛素通过激活Ca(2+)依赖性蛋白激酶C（PKC）亚型并使其膜转位来调节多种上皮细胞的功能。目前尚无关于胰岛素对胆管胆汁分泌调节作用的相关信息。本研究的目的是确定胰岛素在调节胆管结扎（BDL）大鼠胆管细胞分泌中的作用及作用机制。我们确定了胆管细胞中胰岛素受体的亚细胞定位。我们测量了胰岛素对以下方面的影响：（1）在存在或不存在BAPTA/AM、H7或rottlerin的情况下，促胰液素刺激胆管细胞中cAMP水平以及肝内胆管单位（IBDUs）中胆管扩张的影响；（2）胆汁流动的影响。我们评估了：（1）胰岛素的作用是否与PKCα的激活有关；（2）PKC的激活是否导致促胰液素刺激的cAMP水平和蛋白激酶A（PKA）活性受到抑制。我们发现胰岛素受体仅存在于胆管细胞的顶端区域。胰岛素抑制促胰液素诱导的胆汁分泌和促胰液素刺激的胆管细胞cAMP水平。当在基底外侧膜施加胰岛素或微量注射到IBDU管腔中时，胰岛素抑制促胰液素诱导的IBDUs分泌。BAPTA/AM和H7可阻断胰岛素对胆管细胞分泌的抑制作用。胰岛素诱导PKCα的激活，这降低了促胰液素刺激的cAMP和PKA活性。总之，胰岛素通过激活PKC并抑制促胰液素刺激的cAMP和PKA活性，抑制BDL大鼠促胰液素诱导的胆管分泌。总之，在以胆管细胞增殖为特征的BDL模型中，胰岛素对胆管细胞分泌过程具有反向调节作用。
