Park K, Moreland R B, Goldstein I, Atala A, Traish A
Department of Urology, Boston University School of Medicine, Massachusetts 02118, USA.
Biochem Biophys Res Commun. 1998 Aug 28;249(3):612-7. doi: 10.1006/bbrc.1998.9206.
Phosphodiesterases play an important physiological role by regulating the intracellular levels of cyclic nucleotides. In this study, we investigated the kinetic parameters of inhibition of phosphodiesterase (PDE) type 5 (EC 3.1.4.35, 3',5'-cyclic GMP phosphodiesterase) by a novel, high-affinity, selective PDE type 5 inhibitor, sildenafil, in intact cells and in soluble extracts of human clitoral corpus cavernosum smooth muscle cells. Sildenafil inhibited cGMP hydrolysis in the crude extract (Ki = 7.2 +/- 2.7) and in partially purified preparations (Ki = 9 nM) in a competitive manner, as determined by Dixon plots. Sildenafil was a more effective PDE type 5 inhibitor than zaprinast (Ki = 400.0 +/- 76.4 nM, crude extracts; 250 nM, partially purified). Stimulation of intracellular cGMP synthesis by the nitric oxide donor sodium nitroprusside resulted in a 3.3- and 2.9-fold increase in cGMP concentration in the presence of sildenafil or zaprinast, respectively, compared to sodium nitroprusside treatment alone in intact cells at physiological temperatures. These observations suggest that human clitoral corpus cavernosum smooth muscle tone may be regulated by the synthesis and release of nitric oxide and that this pathway is dependent on PDE type 5 activity.
磷酸二酯酶通过调节细胞内环核苷酸水平发挥重要的生理作用。在本研究中，我们研究了一种新型、高亲和力、选择性磷酸二酯酶5（PDE5，EC 3.1.4.35，3',5'-环鸟苷酸磷酸二酯酶）抑制剂西地那非在完整细胞和人阴蒂海绵体平滑肌细胞可溶性提取物中对磷酸二酯酶5的抑制动力学参数。通过狄克逊图测定，西地那非在粗提物（Ki = 7.2 +/- 2.7）和部分纯化制剂（Ki = 9 nM）中以竞争性方式抑制cGMP水解。西地那非是一种比扎普司特更有效的磷酸二酯酶5抑制剂（扎普司特：粗提物中Ki = 400.0 +/- 76.4 nM；部分纯化制剂中Ki = 250 nM）。在生理温度下，与单独使用硝普钠处理完整细胞相比，一氧化氮供体硝普钠刺激细胞内cGMP合成，在存在西地那非或扎普司特的情况下，cGMP浓度分别增加3.3倍和2.9倍。这些观察结果表明，人阴蒂海绵体平滑肌张力可能受一氧化氮的合成和释放调节，且该途径依赖于磷酸二酯酶5的活性。
