title: Vascular smooth muscle sensitivity to varying oxygen tensions, Bay K 8644 and nifedipine.
abstract: With the suggestion that while high oxygen levels may alter the response beyond the receptor, with wrong information about excitation-contraction coupling; it was observed that levels of oxygen affect both the calcium channel blockers and facilitators with net reduction of influx or utilisation of external calcium. In this our study, using rat tail artery activated by noradrenaline and potassium chloride in the presence of Bay K. 8644 and nifedipine at different oxygen levels, we showed that desensitisation of the responses of the vascular smooth muscle occurred. It was evident that the underlying basis of vascular responses observed with different oxygen levels was apparently due to shifting of the control curves. Hence, drugs which modify calcium channels functions may in vitro, be altered qualitatively and quantitatively by hyperoxic conditions, in receptor or voltage sensitive calcium channels, since oxygen appears to exert facilitatory effects on calcium channels.
authors.affiliation: Smooth Muscle Physiology Unit, Department of Physiology, School of Medicine, College of Medical Sciences, University of Benin, Benin City, Nigeria.
authors.forename: A C
authors.initials: AC
authors.lastname: Ugwu
authors.forename: J C
authors.initials: JC
authors.lastname: McGrant
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000818:Animals; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004353:Drug Evaluation, Preclinical; D004361:Drug Tolerance; D018496:Hyperoxia / Q000378:metabolism*; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism*; D009543:Nifedipine / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D011189:Potassium Chloride; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009543:Nifedipine; D010100:Oxygen; D009638:Norepinephrine