Peña-Rasgado C, Kimler V A, McGruder K D, Tie J, Rasgado-Flores H
Department of Physiology and Biophysics, Finch University of Health Sciences, Chicago Medical School, Illinois 60064.
Am J Physiol. 1994 Nov;267(5 Pt 1):C1319-28. doi: 10.1152/ajpcell.1994.267.5.C1319.
It is controversial whether changes in adenosine 3',5'-cyclic monophosphate (cAMP) and in the cAMP-to-guanosine 3',5'-cyclic monophosphate (cGMP) ratio are involved with cell swelling and in the activation of volume-regulatory mechanisms. We examined whether these nucleotides are involved in cell volume regulation in skeletal muscle. Isolated (intact and internally perfused) barnacle muscle cells were used because these cells, when exposed to a hyposmotic environment, undergo an extracellular Ca2+ (Cao)-dependent regulatory volume decrease (RVD). Using intact cells we found that dibutyryl cAMP and forskolin significantly promoted RVD in cells exposed to Cao-free solutions and that dibutyryl cGMP significantly inhibited RVD in cells exposed to Cao-containing solutions. In perfused cells in which the intracellular free Ca2+ concentration ([Ca2+]i) was heavily buffered [with 8 mM ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA)], cAMP induced a volume loss that was inhibited by presence of cGMP. Furthermore, if perfused cells were exposed to hyposmotic conditions, they swelled and underwent RVD provided that [Ca2+]i buffering was low (with 2 mM EGTA). This effect was inhibited by presence of the cAMP antagonist, [R]-p-adenosine 3',5'-cyclic monophosphorothioate.
3',5'-环磷酸腺苷（cAMP）以及cAMP与3',5'-环磷酸鸟苷（cGMP）的比值变化是否与细胞肿胀及容量调节机制的激活有关，这一问题存在争议。我们研究了这些核苷酸是否参与骨骼肌的细胞容量调节。使用分离的（完整的且内部灌注的）藤壶肌细胞，因为这些细胞在暴露于低渗环境时，会经历细胞外Ca2+（Cao）依赖的调节性容积减小（RVD）。利用完整细胞，我们发现二丁酰cAMP和福斯可林显著促进暴露于无Cao溶液中的细胞发生RVD，而二丁酰cGMP显著抑制暴露于含Cao溶液中的细胞发生RVD。在细胞内游离Ca2+浓度（[Ca2+]i）被大量缓冲的灌注细胞中（用8 mM乙二醇双（β-氨基乙醚）-N,N,N',N'-四乙酸（EGTA）），cAMP诱导的容积减小被cGMP的存在所抑制。此外，如果将灌注细胞暴露于低渗条件下，只要[Ca2+]i缓冲较低（用2 mM EGTA），它们就会肿胀并经历RVD。这种效应被cAMP拮抗剂[R]-p-腺苷3',5'-环磷酸硫代酯的存在所抑制。
