Caswell A H, Baker S P, Boyd H, Potter L T, Garcia M
J Biol Chem. 1978 May 10;253(9):3049-54.
Experiments were carried out to clarify the sites of action of beta-adrenergic agonists in skeletal muscle microsomes. Microsomes were fractionated into longitudinal reticulum, terminal cisternae, and isolated transverse tubules. Transverse tubules were selectively labeled and tracked with [3H]ouabain. beta-adrenergic receptor was identified by [3H]dihydroalprenolol binding. Assays of beta-adrenergic receptor, adenylate cyclase, and protein kinase-stimulated phosphorylation showed: 1) beta-adrenergic receptor was detected in transverse tubules with a receptor density of 0.61 pmol/mg of protein. No significant binding was detected in longitudinal reticulum or in terminal cisternae. 2) Isoproterenol-stimulated adenylate cyclase was present in microsomes but was similarly confined to the transverse tubular fraction. The activity of F- stimulated cyclase in transverse tubules was 2.3 nmol/mg of protein/min. 3) No phosphorylation of microsomes by cyclic AMP and protein kinase could be detected. We conclude that the action of epinephrine on skeletal muscle is mediated through receptors and adenylate cyclase in the external membrane.
开展了实验以阐明β - 肾上腺素能激动剂在骨骼肌微粒体中的作用位点。微粒体被分离成长纵网、终末池和分离的横管。横管用[³H]哇巴因进行选择性标记和追踪。β - 肾上腺素能受体通过[³H]二氢心得舒结合来鉴定。对β - 肾上腺素能受体、腺苷酸环化酶和蛋白激酶刺激的磷酸化的测定显示：1）在横管中检测到β - 肾上腺素能受体，受体密度为0.61 pmol/mg蛋白质。在纵网或终末池中未检测到明显的结合。2）异丙肾上腺素刺激的腺苷酸环化酶存在于微粒体中，但同样局限于横管部分。横管中F - 刺激的环化酶活性为2.3 nmol/mg蛋白质/分钟。3）未检测到环磷酸腺苷和蛋白激酶对微粒体的磷酸化作用。我们得出结论，肾上腺素对骨骼肌的作用是通过外膜中的受体和腺苷酸环化酶介导的。
