title: Reversal of nitroglycerin tolerance in vitro by the cGMP-phosphodiesterase inhibitor zaprinast.
abstract: Following in vitro exposure of rat aortic rings to 550 microM nitroglycerin for 1 h, tolerance was demonstrated by a significant increase in EC50 values for nitroglycerin-induced relaxation. However, cross-tolerance to sodium nitroprusside was not observed. Co-incubation of aortic rings with the cGMP-phosphodiesterase (cGMP-PDE) inhibitor zaprinast (10 microM), during incubation with 550 microM nitroglycerin, did not prevent the development of tolerance. However, the addition of 0.30 or 10 microM zaprinast to tolerant aortic rings did restore responsiveness to nitroglycerin. The increase in cGMP in tolerant aortic rings in response to 300 nM nitroglycerin (2-4 fmol/micrograms) was significantly less than that observed for non-tolerant rings (6.6-12 fmol/micrograms), but cGMP levels were restored in tolerant rings by zaprinast (7-12 fmol/micrograms). These data suggest that inhibition of vascular cGMP-PDE activity does not prevent the development of tolerance in vitro, but does reverse the loss of vasorelaxant potency to nitroglycerin via restoration of intracellular cGMP levels.
authors.affiliation: Department of Vascular and Biochemical Pharmacology, Sterling Winthrop Pharmaceuticals Research Division, Collegeville, PA 19426.
authors.forename: E D
authors.initials: ED
authors.lastname: Pagani
authors.forename: G S
authors.initials: GS
authors.lastname: VanAller
authors.forename: B
authors.initials: B
authors.lastname: O'Connor
authors.forename: P J
authors.initials: PJ
authors.lastname: Silver
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000037:antagonists & inhibitors* / Q000302:isolation & purification; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000201:enzymology; D006152:Cyclic GMP / Q000378:metabolism; D004361:Drug Tolerance; D006868:Hydrolysis; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D005996:Nitroglycerin / Q000494:pharmacology*; D011688:Purinones / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D011688:Purinones; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D005996:Nitroglycerin; C011145:zaprinast; D006152:Cyclic GMP