Gettys T W, Blackmore P F, Corbin J D
Howard Hughes Medical Institute, Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee 37232.
Am J Physiol. 1988 Apr;254(4 Pt 1):E449-53. doi: 10.1152/ajpendo.1988.254.4.E449.
The role of phosphodiesterase activation in controlling adenosine 3',5'-cyclic monophosphate (cAMP) levels within hepatocytes was investigated by preloading hepatocytes with the hydrolyzable cAMP analogue 8-para-chlorophenylthio-cAMP (8-pCl phi S-cAMP) and measuring disappearance of the analogue after treating the cells with various hormones. Incubation of hepatocytes with 15 nM 8-pCl phi S-cAMP increased the intracellular concentration of the analogue at 0.5 and 2 min, but by 5 min the concentration plateaued and remained constant or declined slightly at 7 and 10 min. Treatment of hepatocytes with 5 nM glucagon led to a rapid 50% decline in intracellular concentration of the analogue. However, 6 nM insulin produced no detectable change in analogue concentration, and a combination of 5 nM glucagon and 6 nM insulin produced no greater lowering of 8-pCl phi S-cAMP than did glucagon alone. Treatment of hepatocytes with the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (50 microM) blocked approximately 30% of the glucagon-mediated decrease in 8-pCl phi S-cAMP concentration, and in separate cell incubations, it blocked 50% of the cAMP lowering produced by 125 nM 8-pCl phi S-cAMP. Treatment of analogue-preloaded hepatocytes with effective concentrations of phenylephrine, vasopressin, or angiotensin resulted in no change in intracellular analogue or cAMP concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
通过用可水解的环磷酸腺苷（cAMP）类似物8-对氯苯硫基环磷酸腺苷（8-pCl phi S-cAMP）预加载肝细胞，并在细胞用各种激素处理后测量该类似物的消失情况，研究了磷酸二酯酶激活在控制肝细胞内环磷酸腺苷（cAMP）水平中的作用。用15 nM 8-pCl phi S-cAMP孵育肝细胞，在0.5分钟和2分钟时增加了细胞内该类似物的浓度，但到5分钟时浓度达到平稳，在7分钟和10分钟时保持恒定或略有下降。用5 nM胰高血糖素处理肝细胞导致该类似物的细胞内浓度迅速下降50%。然而，6 nM胰岛素对类似物浓度没有可检测到的变化，并且5 nM胰高血糖素和6 nM胰岛素的组合对8-pCl phi S-cAMP的降低作用并不比单独使用胰高血糖素更大。用磷酸二酯酶抑制剂3-异丁基-1-甲基黄嘌呤（50 microM）处理肝细胞可阻断约30%的胰高血糖素介导的8-pCl phi S-cAMP浓度降低，并且在单独的细胞孵育中，它可阻断125 nM 8-pCl phi S-cAMP产生的50%的cAMP降低。用有效浓度的去氧肾上腺素、血管加压素或血管紧张素处理预加载类似物的肝细胞，细胞内类似物或cAMP浓度没有变化。（摘要截断于250字）
