Keppens S, De Wulf H
Biochem J. 1985 Nov 1;231(3):797-99. doi: 10.1042/bj2310797.
Purinergic agonists cause a dose-dependent activation of glycogen phosphorylase in isolated rat hepatocytes. Half-maximally effective concentrations are 5 X 10(-7)M for ATP, 2 X 10(-6)M for ADP, and about 5 X 10(-5) M for AMP and adenosine. This potency series indicates the presence of P2-purinergic receptors. The mode of action of ATP appears to be identical with that of the Ca2+-dependent glycogenolytic hormones angiotensin, vasopressin and alpha 1-adrenergic agonists. (1) They all require Ca2+ for phosphorylase activation; (2) they do not increase cyclic AMP levels; (3) they are susceptible to heterologous desensitization by vasopressin and phenylephrine; (4) they lower cyclic AMP concentrations in hepatocytes stimulated by glucagon, most probably mediated by an enhanced phosphodiesterase activity.
嘌呤能激动剂可使分离的大鼠肝细胞中的糖原磷酸化酶呈剂量依赖性激活。ATP的半数有效浓度为5×10⁻⁷M，ADP为2×10⁻⁶M，AMP和腺苷约为5×10⁻⁵M。这种效能顺序表明存在P2嘌呤能受体。ATP的作用方式似乎与依赖Ca²⁺的糖原分解激素血管紧张素、血管加压素和α1肾上腺素能激动剂相同。（1）它们都需要Ca²⁺来激活磷酸化酶；（2）它们不会增加环磷酸腺苷（cAMP）水平；（3）它们易受血管加压素和去氧肾上腺素的异源脱敏作用影响；（4）它们会降低胰高血糖素刺激的肝细胞中的环磷酸腺苷浓度，这很可能是由增强的磷酸二酯酶活性介导的。
