In situ cardiac performance of Atlantic cod (Gadus morhua) at cold temperatures: long-term acclimation, acute thermal challenge and the role of adrenaline.
The resting and maximum in situ cardiac performance of Newfoundland Atlantic cod (Gadus morhua) acclimated to 10, 4 and 0°C were measured at their respective acclimation temperatures, and when acutely exposed to temperature changes: i.e. hearts from 10°C fish cooled to 4°C, and hearts from 4°C fish measured at 10 and 0°C. Intrinsic heart rate (f(H)) decreased from 41 beats min(-1) at 10°C to 33 beats min(-1) at 4°C and 25 beats min(-1) at 0°C. However, this degree of thermal dependency was not reflected in maximal cardiac output (Q(max) values were ~44, ~37 and ~34 ml min(-1) kg(-1) at 10, 4 and 0°C, respectively). Further, cardiac scope showed a slight positive compensation between 4 and 0°C (Q(10)=1.7), and full, if not a slight over compensation between 10 and 4°C (Q(10)=0.9). The maximal performance of hearts exposed to an acute decrease in temperature (i.e. from 10 to 4°C and 4 to 0°C) was comparable to that measured for hearts from 4°C- and 0°C-acclimated fish, respectively. In contrast, 4°C-acclimated hearts significantly out-performed 10°C-acclimated hearts when tested at a common temperature of 10°C (in terms of both Q(max) and power output). Only minimal differences in cardiac function were seen between hearts stimulated with basal (5 nmol l(-1)) versus maximal (200 nmol l(-1)) levels of adrenaline, the effects of which were not temperature dependent. These results: (1) show that maximum performance of the isolated cod heart is not compromised by exposure to cold temperatures; and (2) support data from other studies, which show that, in contrast to salmonids, cod cardiac performance/myocardial contractility is not dependent upon humoral adrenergic stimulation.
Alfred-Wegener-Institut für Polar- und Meeresforschung, PO Box 120161, 27515 Bremerhaven,  Germany.
Glenn J
GJ
Lurman
Lene H
LH
Petersen
A Kurt
AK
Gamperl
D000064:Acclimatization / Q000187:drug effects / Q000502:physiology*; D000332:Aerobiosis / Q000187:drug effects; D000818:Animals; D002302:Cardiac Output / Q000187:drug effects; D003080:Cold Temperature; D004837:Epinephrine / Q000494:pharmacology*; D005260:Female; D048389:Gadus morhua / Q000502:physiology*; D006321:Heart / Q000187:drug effects* / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D012146:Rest / Q000502:physiology; D013318:Stroke Volume / Q000187:drug effects; D013997:Time Factors
D004837:Epinephrine