氟烷对慢性缺氧兔心肌β肾上腺素能受体的影响

THE EFFECTS OF HALOTHANE ON THE β-ADRENERGIC RECEPTORS OF MYOCARDIUM IN CHRONIC HYPOXIC RABBITS

用放射配基结合法和高效液相色谱电化学法分别测定氟烷对慢性缺氧免心肌β肾上腺素能受体（简称β受体）和血浆儿茶酚胺的影响。结果表明：慢性缺氧后兔心肌β受体密度明显下降，受体亲和力无明显变化，血浆肾上腺素、去甲肾上腺素明显升高。缺氧吸入氟烷后兔心肌β受体密度进一步下降，亲和力增加，血浆肾上腺素、去甲肾上腺素无进一步变化。常氧吸入氟烷后心肌β受体密度无明显变化，亲和力升高，血浆肾上腺素、去甲肾上腺素反而降低。结果提示，氟烷抑制常氧兔交感神经活动而不能抑制缺氧兔交感神经活动，氟烷不改变常氧兔心肌β受体密度，但降低缺氧兔心肌β受体密度。β受体密度降低与缺氧后升高的儿茶酚胺下调β受体数目有关，同时可能与氟烷改变了缺氧心肌细胞膜脂质流动性使受体易向膜内移动有关。

The changes of myocardial β-adrenergic receptors and plasma catecholamines were exam-ined by radioligand binding assay and high performance liquid chromatography separately inchronic hypoxic rabbits after inhalation of halothane.The results showed that the B_(max) ofmyocardium decreased(P<0.05),the Kd of β-adrenoceptors did not change and plasmacatecholamine increased significantly(P<0.001)during hypoxia.When hypoxic rabbits inhaledhalothane,the B_(max) and Kd of β-adrenoceptors reduced further(P<0.05,P<0.01),but plasmacatecholamine showed no further change. When normoxic rabbits inhaled halothane,there wasno alteration in the B_max of β-adrenoceptors,but a significant decrease in the Kd ofβ-adrenoceptors and plasma catecholamines(P<0.05):The results indicate that:(1)halothaneinhibits sympathetic activity in normoxic rabbits,but does not in hypoxic rabbits;(2)halothanedoes not change the B_(max) of myocardial β-adrenoceptors in normoxic rabbits,but reduces it inhypoxic rabbits.The machanism of above aIterations may be attributed to down-regulation ofβ-adrenoceptors by increased concentration of plasma catecholamine. Meanwhile the effect mayalso be mediated by an aIteration of the receptors in the cell membrance due to action ofhalothane on the lipid phase of the membrance.