Curtis D H, Zalin R J
J Cell Physiol. 1985 May;123(2):219-27. doi: 10.1002/jcp.1041230211.
The responsiveness of adenylyl cyclase during avian myogenesis in vitro has been examined. Measurements of cyclic AMP generation in intact cells revealed that the precursor myoblast is highly responsive to prostaglandin E1 (11-fold maximum stimulation); whereas its response to isoproterenol is much smaller (2-fold). From the onset of terminal differentiation, responsiveness to the beta-adrenergic agonist increases progressively, reaching a 5.5-fold maximum response by 96 hr of culture. In contrast, there is little change in the cell population's responsiveness to prostaglandin E1. The rise in catecholamine responsiveness is consistent with previously reported increases in beta-receptors accompanying differentiation. DL-propranolol blocks the response of myoblasts and myotubes to 10(-6) M isoproterenol with the same half maximal inhibition value of 1 X 10(-8) mol. The results also suggest a change in the adrenergic character of the receptors and/or coupling to adenylyl cyclase as myoblasts differentiate. First the alpha-adrenergic antagonist phentolamine (10(-7)-10(-4) mol) inhibits the myoblast's response but enhances that of the myotube. Second, the potency ratios for the responses to isoproterenol, epinephrine, and norepinephrine shift from 1.1:1.0:1.0 in the myoblast to 3.3:2.1:1.0 in the myotube. The findings are discussed with reference to the role of prostaglandins in the positive control of muscle differentiation and the changes in the catecholamine-responsive adenylyl cyclase system as an aspect of the expression of the muscle phenotype.
对体外鸡胚肌生成过程中腺苷酸环化酶的反应性进行了检测。对完整细胞中环磷酸腺苷生成的测量显示，前体细胞成肌细胞对前列腺素E1高度敏感（最大刺激为11倍）；而其对异丙肾上腺素的反应则小得多（2倍）。从终末分化开始，对β-肾上腺素能激动剂的反应性逐渐增加，培养96小时时达到最大反应的5.5倍。相比之下，细胞群体对前列腺素E1的反应性几乎没有变化。儿茶酚胺反应性的增加与先前报道的伴随分化的β-受体增加一致。DL-普萘洛尔以相同的半数最大抑制值1×10⁻⁸mol阻断成肌细胞和肌管对10⁻⁶M异丙肾上腺素的反应。结果还表明，随着成肌细胞分化，受体的肾上腺素能特性和/或与腺苷酸环化酶的偶联发生了变化。首先，α-肾上腺素能拮抗剂酚妥拉明（10⁻⁷ - 10⁻⁴mol）抑制成肌细胞的反应，但增强肌管的反应。其次，对异丙肾上腺素、肾上腺素和去甲肾上腺素反应的效价比从成肌细胞中的1.1:1.0:1.0转变为肌管中的3.3:2.1:1.0。结合前列腺素在肌肉分化的正向调控中的作用以及儿茶酚胺反应性腺苷酸环化酶系统的变化作为肌肉表型表达的一个方面，对这些发现进行了讨论。
