title: Sildenafil inhibits phosphodiesterase type 5 in human clitoral corpus cavernosum smooth muscle.
abstract: 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.
authors.affiliation: Department of Urology, Boston University School of Medicine, Massachusetts 02118, USA.
authors.forename: K
authors.initials: K
authors.lastname: Park
authors.forename: R B
authors.initials: RB
authors.lastname: Moreland
authors.forename: I
authors.initials: I
authors.lastname: Goldstein
authors.forename: A
authors.initials: A
authors.lastname: Atala
authors.forename: A
authors.initials: A
authors.lastname: Traish
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000037:antagonists & inhibitors*; D002478:Cells, Cultured; D002987:Clitoris / Q000098:blood supply / Q000187:drug effects* / Q000201:enzymology*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; D005260:Female; D006801:Humans; D006868:Hydrolysis; D007700:Kinetics; D009126:Muscle Relaxation / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000201:enzymology*; D009569:Nitric Oxide / Q000502:physiology; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D010879:Piperazines / Q000494:pharmacology*; D011687:Purines; D011688:Purinones / Q000494:pharmacology; D000068677:Sildenafil Citrate; D013450:Sulfones
chemical_list: D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D011688:Purinones; D013450:Sulfones; D005576:Colforsin; D009569:Nitric Oxide; D000068677:Sildenafil Citrate; D000242:Cyclic AMP; D010727:Phosphoric Diester Hydrolases; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D054706:Cyclic Nucleotide Phosphodiesterases, Type 5; C517381:PDE5A protein, human; C011145:zaprinast; D006152:Cyclic GMP