Cheng J B, Goldfien A, Cornett L E, Roberts J M
Pediatr Res. 1981 Aug;15(8):1083-7. doi: 10.1203/00006450-198108000-00002.
The fetal sheep heart responds to beta-adrenergic stimuli; however, in vivo studies show the response of the fetal heart is less than that of the adult heart. We used [3H]dihydroalprenolol (DHA) to study directly beta-adrenergic receptors in heart particulates of fetal sheep at term and adult sheep. [3H]DHA binding to fetal heart particulates was rapid, reversible (t 1/2 = 2.9 +/- 0.3 min), stereoselective, saturable (101.2 +/- 7.4 fmoles/mg protein), and of high affinity (4.8 +/- 0.4 nM). The rank order of agonists competing for [3H]DHA binding was isoproterenol (0.32 +/- 0.10 microM) greater than epinephrine (1.19 +/- 0.23 muM) approximately equal to norepinephrine (2.67 +/- 0.69 muM), which is compatible with beta 1-adrenergic potencies. [3H]DHA also bound to the adult sheep heart in a manner expected for beta 1-receptors. No difference in the binding affinity of [3H]DHA or agonists' competition was demonstrated between the fetal and adult sheep heart. Comparison of the concentration of beta-adrenergic receptors in fetal and adult hearts was confounded by the choice of the denominator for unit expression. The concentration was higher in the adult when expressed as a function of protein content or 5'-nucleotidase activity (0.52 +/- 0.07 versus 1.12 +/- 0.06). However, there was no difference when tissue weight, Na+ - K+-ATPase, or NaF-stimulated adenylate cyclase was used. Furthermore, isoproterenol-stimulated adenylate cyclase and cardiac contractile response to a threshold dose of isoproterenol were identical in the fetal and adult sheep heart. We conclude that beta-receptors can be studied with [3H]DHA in the fetal sheep heart, this receptor is qualitatively similar to the beta-receptor in the adult sheep heart, and it is unlikely that there is a difference in the concentration of beta-adrenergic receptors in fetal and adult sheep heart.
胎羊心脏对β-肾上腺素能刺激有反应；然而，体内研究表明，胎儿心脏的反应小于成年心脏。我们使用[3H]二氢阿普洛尔（DHA）直接研究足月胎羊和成年羊心脏微粒中的β-肾上腺素能受体。[3H]DHA与胎羊心脏微粒的结合迅速、可逆（t1/2 = 2.9 +/- 0.3分钟）、具有立体选择性、可饱和（101.2 +/- 7.4飞摩尔/毫克蛋白质）且具有高亲和力（4.8 +/- 0.4纳摩尔）。竞争[3H]DHA结合的激动剂的排序为异丙肾上腺素（0.32 +/- 0.10微摩尔）大于肾上腺素（1.19 +/- 0.23微摩尔）约等于去甲肾上腺素（2.67 +/- 0.69微摩尔），这与β1-肾上腺素能效力相符。[3H]DHA也以β1-受体预期的方式与成年羊心脏结合。在胎羊和成年羊心脏之间，未显示[3H]DHA的结合亲和力或激动剂竞争存在差异。胎羊和成年羊心脏中β-肾上腺素能受体浓度的比较因单位表达分母的选择而混淆。当以蛋白质含量或5'-核苷酸酶活性为函数表示时，成年羊心脏中的浓度较高（0.52 +/- 0.07对1.12 +/- 0.06）。然而，当使用组织重量、Na+-K+-ATP酶或NaF刺激的腺苷酸环化酶时，没有差异。此外，异丙肾上腺素刺激的腺苷酸环化酶以及胎羊和成年羊心脏对阈剂量异丙肾上腺素的心脏收缩反应是相同的。我们得出结论，β-受体可以用[3H]DHA在胎羊心脏中进行研究，该受体在性质上与成年羊心脏中的β-受体相似，并且胎羊和成年羊心脏中β-肾上腺素能受体的浓度不太可能存在差异。
