Matsumoto P S, Mo L, Wills N K
Department of Physiology & Biophysics, University of Texas Medical Branch, Galveston 77555, USA.
J Membr Biol. 1997 Nov 1;160(1):27-38. doi: 10.1007/s002329900292.
Previous work from this laboratory has shown that apical membrane sodium channel activity is stimulated by serosal hyposmotic solutions (Wills, Millinoff & Crowe, 1991). In the present study, we determined whether this stimulation of sodium transport is additive with the actions of prostaglandin E2 (PGE2) or cyclic AMP (cAMP). Addition of exogenous PGE2 (100 nM; serosal bath) to isosmotic solutions led to large increases in the amiloride-sensitive short-circuit current (Isc) and transepithelial conductance (Gt), whereas no significant effects of PGE2 were observed in hyposmotic serosal solutions. Subsequent addition of mucosal amiloride reduced Isc by approximately 95% and Gt by approximately 60%. Inhibition of endogenous PGE2 production by blockers of phospholipase A2 activity (quinacrine or 3[4-octadecyl]-benzoylacrylic acid; OBBA), or inhibition of cyclooxygenase activity by indomethacin reduced the stimulation of Isc and Gt by hyposmotic solutions. Addition of forskolin (FSK) or 3-Isobutyl-1-methylxanthine (IBMX) also resulted in approximately twofold increases in the amiloride-sensitive Isc and Gt and abolished the effects of subsequent hyposmotic challenge. The effects of forskolin, PGE2, and hyposmotic challenge were diminished by pretreatment with H89, a protein kinase A (PKA) inhibitor. We conclude that osmotic regulation of sodium channel activity interacts with multiple intracellular signaling pathways, specifically the arachidonic acid metabolic pathway and the cAMP/PKA intracellular messenger cascade.
该实验室先前的研究表明，浆膜低渗溶液可刺激顶端膜钠通道活性（威尔斯、米利诺夫和克罗，1991年）。在本研究中，我们确定了这种对钠转运的刺激是否与前列腺素E2（PGE2）或环磷酸腺苷（cAMP）的作用相加。向等渗溶液中添加外源性PGE2（100 nM；浆膜浴）导致对氨氯地平敏感的短路电流（Isc）和跨上皮电导（Gt）大幅增加，而在低渗浆膜溶液中未观察到PGE2的显著作用。随后添加黏膜氨氯地平使Isc降低约95%，Gt降低约60%。用磷脂酶A2活性阻滞剂（奎纳克林或3-[4-十八烷基]-苯甲酰丙烯酸；OBBA）抑制内源性PGE2生成，或用吲哚美辛抑制环氧化酶活性，均可降低低渗溶液对Isc和Gt的刺激。添加福斯高林（FSK）或3-异丁基-1-甲基黄嘌呤（IBMX）也导致对氨氯地平敏感的Isc和Gt增加约两倍，并消除了随后低渗刺激的影响。用蛋白激酶A（PKA）抑制剂H89预处理可减弱福斯高林、PGE2和低渗刺激的作用。我们得出结论，钠通道活性的渗透调节与多种细胞内信号通路相互作用，特别是花生四烯酸代谢通路和cAMP/PKA细胞内信使级联反应。
