氟烷抑制离体大鼠脂肪细胞中异丙肾上腺素刺激的脂肪分解的机制。

Mechanism of halothane-induced inhibition of isoproterenol-stimulated lipolysis in isolated rat adipocytes.

作者信息

Prokocimer P G, Maze M, Vickery R G, Kraemer F B, Gandjei R, Hoffman B B

机构信息

Department of Anesthesia, Stanford University School of Medicine, California 94305.

出版信息

Mol Pharmacol. 1988 Mar;33(3):338-43.

PMID:3352597

Abstract

The effect of halothane on isoproterenol-stimulated lipolysis was determined in isolated rat epididymal fat cells. The maximal lipolytic response (Emax) activated by isoproterenol was 350 +/- 61 nmol of glycerol/10(5) cells/hr with an EC50 of 5.1 X 10(-9) M. When the adipocytes were simultaneously bubbled with 2.5% halothane, the Emax decreased to 158 +/- 43 nmol of glycerol/10(5) cells/hr and the dose response curve for isoproterenol was shifted to the right (EC50 3.5 X 10(-8) M, p less than 0.05). When lipolysis was maximally stimulated with (-)-isoproterenol (10(-6)M), the inhibitory effect of halothane was found to be both dose dependent (IC50 approximately 2.5%, v/v) and reversible following washout. Neither the nonhydrolyzable cAMP analog, 8-(4-chlorophenylthio) adenosine 3',5'-cyclic monophosphate (2 X 10(-3)M), nor forskolin (10(-6) M) was able to normalize lipolysis in the presence of halothane. The activation of cAMP-dependent protein kinase (EC 2.7.1.37) activity by isoproterenol was not different in halothane-exposed cells when compared to unexposed cells. When control adipocytes were exposed to isoproterenol (10(-6) M), there was a 2.5-fold increase in the activity of hormone-sensitive lipase (EC 3.1.1.3) from 0.64 +/- 0.13 to 1.53 +/- 0.32 pkat (pmol/sec) per mg (p less than 0.005, n = 10). However, in the presence of halothane (2.5%, v/v) isoproterenol stimulation of hormone-sensitive lipase was attenuated by 50% to values of 1.06 +/- 0.23 pkat/mg (p less than 0.01, n = 10). Halothane had no direct inhibitory effect on hormone-sensitive lipase since this enzyme's activity was unaffected when homogenates of isoproterenol-stimulated control cells were incubated with halothane. These studies suggest that halothane impairs the activation of hormone-sensitive lipase by cAMP-dependent protein kinase and in this manner inhibits beta-adrenergic-stimulated lipolysis.

摘要

在分离的大鼠附睾脂肪细胞中测定了氟烷对异丙肾上腺素刺激的脂肪分解的影响。异丙肾上腺素激活的最大脂肪分解反应（Emax）为350±61 nmol甘油/10⁵细胞/小时，半数有效浓度（EC50）为5.1×10⁻⁹M。当脂肪细胞同时用2.5%氟烷鼓泡时，Emax降至158±43 nmol甘油/10⁵细胞/小时，异丙肾上腺素的剂量反应曲线向右移动（EC50为3.5×10⁻⁸M，p<0.05）。当用（-）-异丙肾上腺素（10⁻⁶M）最大程度刺激脂肪分解时，发现氟烷的抑制作用呈剂量依赖性（半数抑制浓度[IC50]约为2.5%，v/v），冲洗后可逆。在氟烷存在的情况下，不可水解的环磷酸腺苷（cAMP）类似物8-（4-氯苯基硫代）腺苷3',5'-环磷酸（2×10⁻³M）和福斯可林（10⁻⁶M）均无法使脂肪分解恢复正常。与未暴露细胞相比，氟烷暴露细胞中异丙肾上腺素对依赖cAMP的蛋白激酶（EC 2.7.1.37）活性的激活没有差异。当对照脂肪细胞暴露于异丙肾上腺素（10⁻⁶M）时，激素敏感性脂肪酶（EC 3.1.1.3）的活性从0.64±0.13增加到1.53±0.32 pkat（pmol/秒）/毫克，增加了2.5倍（p<0.005，n = 10）。然而，在氟烷（2.5%，v/v）存在的情况下，异丙肾上腺素对激素敏感性脂肪酶的刺激作用减弱了50%，降至1.06±0.23 pkat/毫克（p<0.01，n = 10）。氟烷对激素敏感性脂肪酶没有直接抑制作用，因为当异丙肾上腺素刺激的对照细胞匀浆与氟烷一起孵育时，该酶的活性不受影响。这些研究表明，氟烷损害了依赖cAMP的蛋白激酶对激素敏感性脂肪酶的激活，从而抑制了β-肾上腺素能刺激的脂肪分解。