title: Isoproterenol-induced maximal heart rate in normothermic and hyperthermic horses.
abstract: The heart rate (HR) induced by maximal beta-adrenergic activation, which was elicited by infusion of isoproterenol, was studied in 8 healthy horses before (control) and after hyperthermia was induced by IV administration of 2,4-dinitrophenol (DNP). Isoproterenol was administered IV at 1.0 micrograms.kg-1.min-1 for 3 minutes, and the HR was determined during the final 30 seconds of the infusion. As the rectal temperature increased (P less than 0.001) from 38.2 +/- 0.1 C (mean +/- SEM; normothermic control) to 40.1 +/- 0.1 C at 60 minutes after DNP administration, the isoproterenol-induced HR also increased from 198 +/- 4 beats/min (control) to 214 +/- 4 beats/min (P less than 0.001). It appeared that the values of HR achieved with maximal beta-adrenergic activation were augmented by the hypermetabolic, hyperthermic state induced by DNP.
authors.affiliation: Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana 61801.
authors.forename: T E
authors.initials: TE
authors.lastname: Goetz
authors.forename: M
authors.initials: M
authors.lastname: Manohar
mesh_terms: D019297:2,4-Dinitrophenol; D000818:Animals; D001831:Body Temperature / Q000187:drug effects; D004140:Dinitrophenols; D005260:Female; D005334:Fever / Q000139:chemically induced / Q000503:physiopathology / Q000662:veterinary*; D006339:Heart Rate / Q000187:drug effects*; D006734:Horse Diseases / Q000139:chemically induced / Q000503:physiopathology*; D006736:Horses / Q000502:physiology*; D007262:Infusions, Intravenous / Q000662:veterinary; D007545:Isoproterenol / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D013997:Time Factors
chemical_list: D004140:Dinitrophenols; D007545:Isoproterenol; D019297:2,4-Dinitrophenol