Morita T, Sakata K, Kanagawa A, Ueki H
Department of Biochemistry, Faculty of Pharmacy and Pharmaceutical Sciences, Fukuyama University, Japan.
Biol Pharm Bull. 1994 May;17(5):577-80. doi: 10.1248/bpb.17.577.
The release of hepatic triacylglyceride lipase [EC 3.1.1.3] has been examined in isolated hepatocytes in primary culture. The stimulatory release of activity from the hepatocytes into the medium by sodium orthovanadate (vanadate) was observed in a time- and dose-dependent manner. However, insulin failed to have this stimulatory action. Moreover, vanadate rapidly increased the cyclic adenosine monophosphate (cyclic AMP) content in hepatocytes in a time- and dose-dependent manner. The treatment of hepatocytes with H-89, which is a potent cyclic AMP-dependent protein kinase inhibitor, decreased the stimulatory release of hepatic lipase activity by vanadate. The vanadate-stimulated release of the enzyme activity was suppressed by uncouplers. In addition, the incorporation of [3H]leucine into protein was increased in the presence of vanadate. Under the marked inhibition of protein synthesis by cycloheximide, vanadate still showed a full effect on the release of the enzyme activity. These results suggest that the vanadate-stimulated release of hepatic lipase activity from the cultured hepatocytes is associated with a rapid increase in intracellular cyclic AMP content, probably due to an activation of cyclic AMP-dependent protein kinase which requires a metabolic energy process rather than an elevation in enzyme molecule synthesis.
在原代培养的分离肝细胞中，已对肝甘油三酯脂肪酶[EC 3.1.1.3]的释放进行了研究。观察到原钒酸钠（钒酸盐）以时间和剂量依赖性方式刺激肝细胞中的活性释放到培养基中。然而，胰岛素未能产生这种刺激作用。此外，钒酸盐以时间和剂量依赖性方式迅速增加肝细胞中的环磷酸腺苷（环AMP）含量。用强效环AMP依赖性蛋白激酶抑制剂H-89处理肝细胞，可降低钒酸盐对肝脂肪酶活性的刺激释放。钒酸盐刺激的酶活性释放被解偶联剂抑制。此外，在钒酸盐存在下，[3H]亮氨酸掺入蛋白质的量增加。在环己酰亚胺对蛋白质合成的显著抑制下，钒酸盐对酶活性的释放仍显示出完全的作用。这些结果表明，钒酸盐刺激培养肝细胞中肝脂肪酶活性的释放与细胞内环AMP含量的迅速增加有关，这可能是由于环AMP依赖性蛋白激酶的激活，而这需要代谢能量过程，而非酶分子合成的增加。
