糖皮质激素和儿茶酚胺对大鼠肝细胞氨基酸转运的刺激作用。高亲和力成分的合成。

Glucocorticoid and catecholamine stimulation of amino acid transport in rat hepatocytes. Synthesis of a high-affinity component.

作者信息

Canivet B, Fehlmann M, Freychet P

出版信息

Mol Cell Endocrinol. 1980 Sep;19(3):253-61. doi: 10.1016/0303-7207(80)90055-6.

Abstract

The kinetic properties of glucocorticoid and catecholamine stimulation of amino acid transport in freshly isolated rat hepatocytes were investigated. In the basal state (i.e., with hepatocytes incubated for 2 h in the absence of glucocorticoid or catecholamine), the saturable transport of alpha-aminoisobutyric acid (AIB) was accounted for mainly by a low-affinity component (Km for AIB approximately 5 mM). Hepatocyte exposure to cortisol (or dexamethasone), or to epinephrine for isoproterenol), for 2 h resulted in a 3- to 4-fold increase in the Vmax of a high-affinity component (Km for AIB approximately 1 mM) which was only weakly expressed in the basal state. Neither glucocorticoids nor catecholamines exerted a detectable effect on the low-affinity transport component. Cycloheximide prevented the emergence of the high-affinity component in hepatocytes exposed to dexamethasone or epinephrine. The results suggest that the stmulatory effect of glucocorticoids and catecholamines on amino acid transport in hepatocytes results from the synthesis of a high-affinity transport component.

摘要

研究了糖皮质激素和儿茶酚胺对新鲜分离的大鼠肝细胞氨基酸转运的刺激动力学特性。在基础状态下（即肝细胞在无糖皮质激素或儿茶酚胺的情况下孵育2小时），α-氨基异丁酸（AIB）的可饱和转运主要由低亲和力成分（AIB的Km约为5 mM）介导。肝细胞暴露于皮质醇（或地塞米松）或肾上腺素（或异丙肾上腺素）2小时后，高亲和力成分（AIB的Km约为1 mM）的Vmax增加了3至4倍，而该成分在基础状态下表达较弱。糖皮质激素和儿茶酚胺对低亲和力转运成分均未产生可检测到的影响。环己酰亚胺可阻止暴露于地塞米松或肾上腺素的肝细胞中高亲和力成分的出现。结果表明，糖皮质激素和儿茶酚胺对肝细胞氨基酸转运的刺激作用是由高亲和力转运成分的合成所致。