title: Syntheses, calcium channel agonist-antagonist modulation activities, nitric oxide release, and voltage-clamp studies of 2-nitrooxyethyl 1,4-dihydro- 2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)pyridine-5-carboxylate enantiomers.
abstract: The novel (-)-(S)-2 and (+)-(R)-3 enantiomers of 2-nitrooxyethyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)pyridine-5-carboxylate were synthesized for evaluation as calcium channel modulators. Determination of their in vitro calcium-channel-modulating activities using guinea pig left atria (GPLA) and ileum longitudinal smooth muscle (GPILSM) showed that the (-)-(S)-2 enantiomer acted as a dual cardioselective calcium channel agonist (GPLA)/smooth muscle selective calcium channel antagonist (GPILSM). In contrast, the (+)-(R)-3 enantiomer exhibited calcium channel antagonist activity on both GPLA and GPILSM. The 2-nitrooxyethyl racemate is a nitric oxide (.NO) donor that released 2.7% .NO, relative to the reference drug glyceryl trinitrate (5.3% .NO release/ONO(2) moiety), in the presence of N-acetylcysteamine. Whole-cell voltage-clamp studies using isolated guinea pig ventricular myocytes indicated that both enantiomers inhibit calcium current but that the (-)-(S)-2 enantiomer is a weaker antagonist than the (+)-(R)-3 enantiomer. These results indicate that replacement of the methyl ester substituent of (-)-(S)-methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)pyridine-5-carboxylate [(-)-(S)-1] by the 2-nitrooxyethyl ester .NO donor substituent present in (-)-(S)-2 provides a useful drug design concept to abolish the contraindicated calcium channel agonist effect of (-)-(S)-1 on vascular smooth muscle. The novel (-)-(S)-2 enantiomer is a useful lead compound for drug discovery targeted toward the treatment of congestive heart failure, and it provides a useful probe to study the structure-function relationships of calcium channels.
authors.affiliation: Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta T6G 2N8, Canada.
authors.forename: Rudong
authors.initials: R
authors.lastname: Shan
authors.forename: Susan E
authors.initials: SE
authors.lastname: Howlett
authors.forename: Edward E
authors.initials: EE
authors.lastname: Knaus
mesh_terms: D000818:Animals; D002120:Calcium Channel Agonists / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D009206:Myocardium / Q000166:cytology; D009539:Nicotinic Acids / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D009569:Nitric Oxide / Q000737:chemistry*; D018408:Patch-Clamp Techniques; D011725:Pyridines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D013237:Stereoisomerism
chemical_list: C121908:2-nitrooxyethyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluoromethylphenyl)pyridine-5-carboxylate; D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D009539:Nicotinic Acids; D011725:Pyridines; D009569:Nitric Oxide