In situ cardiac performance of Atlantic cod (Gadus morhua) at cold temperatures: long-term acclimation, acute thermal challenge and the role of adrenaline.
JOURNAL OF EXPERIMENTAL BIOLOGY(2012)
摘要
The resting and maximum in situ cardiac performance of Newfoundland Atlantic cod (Gadus morhua) acclimated to 10, 4 and 0 degrees C were measured at their respective acclimation temperatures, and when acutely exposed to temperature changes: i.e. hearts from 10 degrees C fish cooled to 4 degrees C, and hearts from 4 degrees C fish measured at 10 and 0 degrees C. Intrinsic heart rate (f(H)) decreased from 41 beats min(-1) at 10 degrees C to 33 beats min(-1) at 4 degrees C and 25 beats min(-1) at 0 degrees C. However, this degree of thermal dependency was not reflected in maximal cardiac output (Q(max) values were similar to 44, similar to 37 and similar to 34 ml min(-1) kg(-1) at 10, 4 and 0 degrees C, respectively). Further, cardiac scope showed a slight positive compensation between 4 and 0 degrees C (Q(10)=1.7), and full, if not a slight over compensation between 10 and 4 degrees C (Q(10)=0.9). The maximal performance of hearts exposed to an acute decrease in temperature (i.e. from 10 to 4 degrees C and 4 to 0 degrees C) was comparable to that measured for hearts from 4 degrees C- and 0 degrees C-acclimated fish, respectively. In contrast, 4 degrees C-acclimated hearts significantly out-performed 10 degrees C-acclimated hearts when tested at a common temperature of 10 degrees 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.
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关键词
cod,heart,heart rate,cardiac output,temperature,adrenergic stimulation,catecholamines
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