Lehotay D C, Murphy B E
Endocr Res Commun. 1975;2(6-7):431-43. doi: 10.1080/07435807509084165.
Plasma membranes were isolated from bovine renal cortex. This particulate, adenylate cyclase-containing fraction was stimulated to produce cyclic AMP by parathyroid hormone and fluoride. When the time-course of adenylate cyclase activity was investigated, it was found that while PTH-stimulated cyclic AMP production comes to a halt in about 15 minutes after the initiation of the reaction, fluoride-stimulated activity continues unabated for at least an hour. Experiments to determine the cause of this showed that the cyclase enzyme is not degraded under our experimental conditions, but is inhibited by a soluble, unbound product of the reaction which requires ATP for its synthesis. In our experiments degradation of parathyroid hormone was relatively slow and could not account for the rapid inhibition of PTH-stimulated cyclase activity. Of the various agents tested, cyclic AMP was found capable of inhibiting PTH-stimulated cyclic AMP production by our purified membrane preparation. Half-maximal inhibition was observed at around 10(-6) M concentrations of the nucleotide. Pyrophosphate, adenosine, 5'-AMP and ADP had no effects. The significance of these results in relation to the regulation of adenylate cyclase activity is discussed.
从牛肾皮质中分离出质膜。这个含有颗粒状腺苷酸环化酶的部分被甲状旁腺激素和氟化物刺激产生环磷酸腺苷（cAMP）。当研究腺苷酸环化酶活性的时间进程时，发现甲状旁腺激素刺激的cAMP产生在反应开始后约15分钟停止，而氟化物刺激的活性至少持续一小时未减弱。确定其原因的实验表明，在我们的实验条件下，环化酶不会降解，而是被反应的一种可溶性、未结合产物抑制，该产物的合成需要ATP。在我们的实验中，甲状旁腺激素的降解相对较慢，无法解释甲状旁腺激素刺激的环化酶活性的快速抑制。在测试的各种试剂中，发现环磷酸腺苷能够通过我们纯化的膜制剂抑制甲状旁腺激素刺激的环磷酸腺苷产生。在核苷酸浓度约为10^(-6) M时观察到半数最大抑制。焦磷酸、腺苷、5'-腺苷酸和二磷酸腺苷没有作用。讨论了这些结果与腺苷酸环化酶活性调节的关系。
