title: Effects of temperature and calcium availability on ventricular myocardium from rainbow trout.
abstract: We studied the mechanical and electrophysiological properties of ventricular myocardium from rainbow trout (Oncorhynchus mykiss) in vitro at 4, 10, and 18 degrees C from fish acclimated at 10 degrees C. Temperature alone did not significantly alter the contractile force of the myocardium, but the time to peak tension and time to 80% relaxation were prolonged at 4 degrees C and shortened at 18 degrees C. The duration of the action potential was also prolonged at 4 degrees C and progressively shortened at higher temperatures. An alteration of the stimulation frequency did not affect contraction amplitude at any temperature. Calcium influx via L-type calcium channels was increased by raising extracellular calcium concentration (¿Ca(2+)(o)) or including Bay K 8644 (Bay K) and isoproterenol in the bathing medium. These treatments significantly enhanced the contractile force at all temperatures. Calcium channel blockers had a reverse-negative inotropic effect. Unexpectedly, the duration of the action potential at 10 degrees C was shortened as ¿Ca(2+)(o) increased. However, Bay K prolonged the plateau phase at 4 degrees C. Caffeine, which promotes the release of sarcoplasmic reticulum (SR) calcium, increased contractile force eightfold at all three temperatures, but the SR blocker ryanodine was only inhibitory at 4 degrees C. Our results suggest that contractile force in ventricular myocardium from Oncorhynchus mykiss is primarily regulated by sarcolemmal calcium influx and that ventricular contractility is maintained during exposure to a wide range of temperatures.
authors.affiliation: Department of Biological Sciences, Wellesley College, Wellesley, MA 2481-8203, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Coyne
authors.forename: C S
authors.initials: CS
authors.lastname: Kim
authors.forename: J S
authors.initials: JS
authors.lastname: Cameron
authors.forename: J K
authors.initials: JK
authors.lastname: Gwathmey
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001831:Body Temperature / Q000502:physiology*; D002104:Cadmium / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000493:pharmacokinetics*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000378:metabolism; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D003080:Cold Temperature; D006352:Heart Ventricles / Q000187:drug effects; D007537:Isometric Contraction / Q000187:drug effects / Q000502:physiology; D007545:Isoproterenol / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects* / Q000502:physiology*; D009206:Myocardium / Q000737:chemistry / Q000378:metabolism; D009529:Nicardipine / Q000494:pharmacology; D017686:Oncorhynchus mykiss / Q000502:physiology*; D010101:Oxygen Consumption / Q000502:physiology; D018408:Patch-Clamp Techniques; D012433:Ryanodine / Q000494:pharmacology; D012508:Sarcolemma / Q000737:chemistry / Q000378:metabolism; D016276:Ventricular Function
chemical_list: D000318:Adrenergic beta-Agonists; D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D000697:Central Nervous System Stimulants; D002104:Cadmium; D012433:Ryanodine; D002110:Caffeine; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009529:Nicardipine; D007545:Isoproterenol; D002118:Calcium