Lönnroth P, Smith U
Biochem Biophys Res Commun. 1983 May 16;112(3):972-9. doi: 10.1016/0006-291x(83)91713-8.
In order to study factors regulating insulin binding to rat adipocytes short- and long-term incubations were performed in the presence or absence of noradrenaline (NA) at a concentration of 3 microM. Culture with NA for 24 hours resulted in a significant decrease (30%) of insulin binding due to a reduced number of binding sites. This reduction was dose-dependent and completely prevented by the addition of timolol, a beta-adrenergic blocking agent, but not by the alpha-blocking agent phentolamine. Addition of 1.0 mM db cAMP to the culture medium resulted in a similar reduction in insulin binding. Also short-term incubations with NA resulted in a downregulation of insulin binding; reproducible reductions seen already after 20 min and about 30% reduction achieved after 2 hours' preincubation. Thus, beta-adrenergic stimulation and subsequent cAMP elevation results in a rapid reduction in the number of insulin binding sites.
为了研究调节胰岛素与大鼠脂肪细胞结合的因素，在存在或不存在浓度为3微摩尔的去甲肾上腺素（NA）的情况下进行了短期和长期孵育。用NA培养24小时导致胰岛素结合显著减少（30%），原因是结合位点数量减少。这种减少是剂量依赖性的，并且通过添加β-肾上腺素能阻断剂噻吗洛尔可完全防止，但α-阻断剂酚妥拉明则不能。向培养基中添加1.0 mM二丁酰环磷腺苷（db cAMP）导致胰岛素结合出现类似的减少。用NA进行短期孵育也导致胰岛素结合下调；在预孵育20分钟后就已出现可重复的减少，预孵育2小时后减少约30%。因此，β-肾上腺素能刺激和随后的环磷腺苷（cAMP）升高导致胰岛素结合位点数量迅速减少。
