Issekutz T B
Am J Physiol. 1975 Aug;229(2):291-7. doi: 10.1152/ajplegacy.1975.229.2.291.
The turnover rate of plasma cAMP was measured in unanesthetized normal and methylprednisolone (MP)-treated dogs with [8-3H]cAMP. Determination of specific activity was based on saturation of the specific binding protein, thus bypassing the need to know the plasma level of cAMP. In normal dogs the infusion of epinephrine increased plasma glucose by 33% and both the plasma level and rate of appearance (Ra) of cAMP 2.5-fold. Treatment with MP decreased the concentration as well as the turnover rate of cAMP by about 50%. It greatly potentiated not only the hyperglycemic effect (4-fold) of epinephrine but also the rise of plasma cAMP (8.5-fold) and that of Ra (6.8-fold). Norepinephrine infusion increased cAMP only by 50%. This effect was not potentiated by MP treatment and not altered by Na nicotinate. There was a linear correlation between plasma cAMP concentration and the rate of disappearance (Rd) of cAMP. It is concluded that: a) the increase of hepatic glycogenolysis is accompanied by a rise of cAMP output, whereas that of lipolysis is not; b) glucocorticoid treatment affects cAMP turnover; and c) the plasma level of cAMP is controlled by Ra, whereas Rd is the result of the mass-action effect of the concentration.
用[8-3H]环磷腺苷（cAMP）测定了未麻醉的正常犬和甲基强的松龙（MP）处理犬的血浆cAMP周转率。比活性的测定基于特异性结合蛋白的饱和，从而无需了解cAMP的血浆水平。在正常犬中，输注肾上腺素使血浆葡萄糖增加33%，cAMP的血浆水平和生成速率（Ra）均增加2.5倍。MP处理使cAMP的浓度和周转率降低约50%。它不仅极大地增强了肾上腺素的高血糖作用（4倍），还增强了血浆cAMP的升高（8.5倍）和Ra的升高（6.8倍）。输注去甲肾上腺素仅使cAMP增加50%。MP处理未增强此作用，烟酸也未改变此作用。血浆cAMP浓度与cAMP的消失速率（Rd）之间存在线性关系。结论如下：a）肝糖原分解增加伴随着cAMP输出增加，而脂肪分解增加则不然；b）糖皮质激素处理影响cAMP周转；c）cAMP的血浆水平受Ra控制，而Rd是浓度质量作用效应的结果。
