Cernohorský M, Hynie S
Farmakologický ústav 1. lékarské fakulty Univerzity Karlovy, Praha, Czech Republic.
Sb Lek. 1993;94(1):63-70.
Oestradiol administration in vivo has been shown to potentiate the adrenergic lipolysis in vitro in rat epididymal adipose tissue; one of the possible explanations of this oestradiol effect might be the direct influencing of beta-adrenergic receptors. In order to show this possible mechanism of action, in direct radioligand binding studies we have estimated the specific binding parameters of beta-adrenergic receptors in controls and in vivo pretreated rats by a single dose of oestrogen (200 microgram.kg-1 s.c. 24 hours prior sacrification of rats). Beta-adrenergic receptor binding studies we performed with membrane fraction of homogenates of epididymal adipose cells, the radioligand used was L-[3H]-dihydroalprenolol (3H-DHA). No clear-cut differences in the saturation curves of 3H-DHA were found between control and pretreated oestradiol rats; the density of beta-adrenoreceptors (Bmax) was practically identical (269 v. 270 fmol.mg-1 protein) and also differences in dissociation constants (Kd) of both groups were minimal (1.05 vs. 0.95 nmol.1-1). Minimal differences between control and oestradiol pretreated rats were also found in displacement studies, where the effects of 1-isomers of norepinephrine and epinephrine was tested. Thus, it seems possible that the potentiating effect of in vivo pretreatment by oestradiol on adrenergic lipolysis of epididymal adipose tissue in vitro is not caused by the direct influencing of beta-adrenergic receptors. The explanation of this effect will be necessary to search on other steps of the adrenergic reaction which lead to lipolysis or in influencing other receptors (e.g. alpha-adrenergic receptors).
体内给予雌二醇已被证明可增强大鼠附睾脂肪组织体外肾上腺素能脂肪分解作用；这种雌二醇效应的一种可能解释可能是对β-肾上腺素能受体的直接影响。为了证明这种可能的作用机制，在直接放射配体结合研究中，我们通过单剂量雌激素（在处死大鼠前24小时皮下注射200微克·千克⁻¹）对对照组和体内预处理大鼠的β-肾上腺素能受体的特异性结合参数进行了估计。我们用附睾脂肪细胞匀浆的膜部分进行β-肾上腺素能受体结合研究，所用的放射配体是L-[³H]-二氢阿普洛尔（³H-DHA）。在对照组和预处理雌二醇大鼠之间未发现³H-DHA饱和曲线有明显差异；β-肾上腺素能受体的密度（Bmax）实际上是相同的（269对270飞摩尔·毫克⁻¹蛋白质），两组的解离常数（Kd）差异也最小（1.05对0.95纳摩尔·升⁻¹）。在置换研究中，测试了去甲肾上腺素和肾上腺素的1-异构体的作用，在对照组和预处理雌二醇大鼠之间也发现了最小差异。因此，体内用雌二醇预处理对体外附睾脂肪组织肾上腺素能脂肪分解的增强作用似乎不是由对β-肾上腺素能受体的直接影响引起的。有必要在导致脂肪分解的肾上腺素能反应的其他步骤或对其他受体（如α-肾上腺素能受体）的影响方面寻找这种效应的解释。
