title: Enhancement in myocardial inotropic response to BAY K 8644 with advancing age.
abstract: In the present study, age-related alterations in cardiovascular response to Ca2+ agonist BAY K 8644 were investigated in rats. Dose response of BAY K 8644 (1-30 micrograms/kg) was studied in open chest rats by intravenous bolus administration. Maximum elevation of mean arterial pressure and (+)dp/dt of left ventricular pressure were significantly higher and the dose of BAY K 8644 required to produce half maximal response was substantially lower in 12 months old (4 micrograms/kg) than in 2 months old (10 micrograms/kg) rats. Larger doses of BAY K 8644 produced arrhythmias only in 12 months old rats, which was not totally abolished by nitroglycerine pretreatment. Perfusion of isolated rat hearts with 10(-6) M BAY K 8644 produced positive inotropic response, which was on the average 50% greater and developed much faster in 12 months old than in 2 months old rats. It is therefore concluded that the myocardial sensitivity to BAY K 8644 increases during adult maturation.
authors.affiliation: Department of Medicine, University of Manitoba, Winnipeg, Canada.
authors.forename: J C
authors.initials: JC
authors.lastname: Khatter
authors.forename: S
authors.initials: S
authors.lastname: Navaratnam
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000375:Aging / Q000502:physiology*; D000818:Animals; D001145:Arrhythmias, Cardiac / Q000139:chemically induced; D001794:Blood Pressure / Q000187:drug effects; D015220:Calcium Channels / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D015220:Calcium Channels; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009543:Nifedipine