Lafontan M, Berlan M, Carpene C
Int J Obes. 1985;9 Suppl 1:117-27.
The present review summarizes recent data on fat cell adrenoceptors with the aim of clarifying the role played by catecholamines in the regulation of adipocyte metabolism. Part of the review is focused on the possible interest of animal models for the study of catecholamine-mediated effects in human fat cells. It is now clearly demonstrated that human, hamster, dog and rabbit fat cells possess three basic types of adrenoceptor: the beta 1-, alpha 2- and alpha 1-adrenoceptors identified in biological assays or binding studies with selected radioligands. The rat is an exception in the species commonly studied as catecholamines exert an exclusive lipolytic effect through beta-adrenoceptor stimulation, there are no alpha 2-adrenoceptors in rat white fat cells although an alpha 1-adrenoceptor does exist. In human fat cells, physiological amines are lipolytic or antilipolytic. Binding studies have revealed that alpha 2-adrenoceptors are three to four times more numerous than beta 1-adrenoceptors. Moreover physiological amines, in particular epinephrine, have a higher affinity for alpha 2-sites than for beta 1-sites. Dose-response studies of the effect of epinephrine on adenosine-deaminase or isoproterenol-stimulated fat-cells demonstrate an inhibitory effect of epinephrine on lipolysis promoted by stimulation of alpha 2-adrenoceptors which occurs before the commonly described beta 1-adrenergic effect which promotes stimulation of lipolysis. This aspect and its putative physiological interest is described and discussed. Intraspecific variations in adrenergic responses of adipocytes have been briefly analysed. The appearance and disappearance of alpha 2-adrenoceptors according to the extent of adipose tissue and increment of fat cell size are discussed. Variations of adrenergic responsiveness during fasting, calorie restriction or chronic stimulation of the adipocytes by physiological amines are also discussed.
本综述总结了关于脂肪细胞肾上腺素能受体的最新数据，旨在阐明儿茶酚胺在调节脂肪细胞代谢中所起的作用。综述的一部分重点关注动物模型对于研究儿茶酚胺介导的人类脂肪细胞效应的潜在价值。现已明确证实，人类、仓鼠、犬和兔的脂肪细胞具有三种基本类型的肾上腺素能受体：通过生物学测定或与选定放射性配体的结合研究鉴定出的β1-、α2-和α1-肾上腺素能受体。在常见研究的物种中，大鼠是个例外，因为儿茶酚胺通过刺激β-肾上腺素能受体发挥唯一的脂解作用，大鼠白色脂肪细胞中不存在α2-肾上腺素能受体，不过α1-肾上腺素能受体确实存在。在人类脂肪细胞中，生理性胺类具有脂解或抗脂解作用。结合研究表明，α2-肾上腺素能受体的数量比β1-肾上腺素能受体多三到四倍。此外，生理性胺类，尤其是肾上腺素，对α2-位点的亲和力高于对β1-位点的亲和力。肾上腺素对腺苷脱氨酶或异丙肾上腺素刺激的脂肪细胞作用的剂量反应研究表明，肾上腺素对由α2-肾上腺素能受体刺激促进的脂解具有抑制作用，这一作用发生在通常描述的促进脂解的β1-肾上腺素能效应之前。这一方面及其假定的生理意义将予以描述和讨论。已简要分析了脂肪细胞肾上腺素能反应的种内差异。讨论了根据脂肪组织范围和脂肪细胞大小增加情况，α2-肾上腺素能受体的出现和消失。还讨论了禁食、热量限制或生理性胺类对脂肪细胞的慢性刺激过程中肾上腺素能反应性的变化。
