Miot F, Keppens S, Erneux C, Wells J N, De Wulf H
Afdeling Biochemie, Fakulteit der Geneeskunde, Katholieke Universiteit, Leuven, Belgium.
Biochem Pharmacol. 1988 Sep 15;37(18):3447-53. doi: 10.1016/0006-2952(88)90695-8.
Vasopressin has been shown previously to lower the glucagon-induced increase of cyclic AMP levels in isolated rat hepatocytes by way of an enhanced phosphodiesterase (EC 3.1.4.17) activity. Five phosphodiesterase inhibitors were tested for their ability to prevent vasopressin from lowering cyclic AMP levels in intact hepatocytes and for their inhibitory effect in vitro on soluble and particulate phosphodiesterase activities partially purified from hepatocytes. Three soluble activities have been separated by DEAE-cellulose chromatography: a phosphodiesterase hydrolyzing both cyclic AMP and cyclic GMP, a form stimulated by cyclic GMP and a cyclic AMP-specific activity. The absence of any statistically significant correlation between the in vivo (in intact cells) and the in vitro (on isolated phosphodiesterases) potencies of the inhibitors does not support a role for the cytosolic phosphodiesterases in mediating the vasopressin-induced decrease in cyclic AMP levels. No statistically significant correlation was observed between the inhibition of the vasopressin effect on cyclic AMP accumulation and the inhibition of phosphodiesterase activity either associated with the native plasma membranes or solubilized from these membranes with 0.4 M NaCl. In contrast, a statistically significant correlation was observed between the degree of inhibition of the vasopressin effect in the intact cells and the degree of inhibition of the intrinsic phosphodiesterase still associated with the plasma membranes after high-salt treatment. These data indicate that a phosphodiesterase activity integral to the plasma membrane is very likely involved in the negative control of cyclic AMP levels by vasopressin.
先前的研究表明，血管加压素可通过增强磷酸二酯酶（EC 3.1.4.17）的活性，降低胰高血糖素诱导的离体大鼠肝细胞中环磷酸腺苷（cAMP）水平的升高。测试了五种磷酸二酯酶抑制剂，观察它们防止血管加压素降低完整肝细胞中cAMP水平的能力，以及它们在体外对从肝细胞中部分纯化的可溶性和颗粒性磷酸二酯酶活性的抑制作用。通过DEAE-纤维素色谱法分离出三种可溶性活性：一种可水解cAMP和环磷酸鸟苷（cGMP）的磷酸二酯酶、一种受cGMP刺激的形式以及一种cAMP特异性活性。抑制剂在体内（在完整细胞中）和体外（对分离的磷酸二酯酶）效力之间不存在任何统计学上的显著相关性，这并不支持胞质磷酸二酯酶在介导血管加压素诱导的cAMP水平降低中发挥作用。在血管加压素对cAMP积累的作用抑制与对天然质膜相关的或用0.4 M NaCl从这些膜中溶解的磷酸二酯酶活性的抑制之间，未观察到统计学上的显著相关性。相反，在完整细胞中血管加压素作用的抑制程度与高盐处理后仍与质膜相关的内在磷酸二酯酶的抑制程度之间，观察到统计学上的显著相关性。这些数据表明，质膜不可或缺的一种磷酸二酯酶活性很可能参与了血管加压素对cAMP水平的负调控。
