Atlantic cod (Gadus morhua L.) in situ cardiac performance at cold temperatures: long-term acclimation, acute thermal challenge and the role of adrenaline

Abstract

SUMMARYThe 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 ) 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.

Seasonal changes in the behaviour and respiration physiology of the freshwater duck musselAnodonta anatina.

“…In the muscle itself, there can be changes in ion channel function (McArdle and Johnston, 1982;Godiksen and Jessen, 2002) as well as changes in muscle fibre protein composition (Johnston and Temple, 2002;Tattersall et al, 2012) and recruitment order (Rome, 1990;Catalán et al, 2004). At a physiological level, there are also changes in cardiac function (Keen and Farrell, 1994;Lurman et al, 2012). These factors combined lead to maintained swimming performance despite changes in temperature, and thus maintained ability to out-swim predators or catch prey.…”

Cold acclimation increases cardiac myofilament function and ventricular pressure generation in trout

“…The above changes all contribute to cardiac contractility and how it is maintained at low temperatures. Supporting this idea, Graham and Farrell (Graham and Farrell, 1989) demonstrated that maximum cardiac work is similar for rainbow trout acclimated to 5 or 15°C, and Lurman et al (Lurman et al, 2012) found little difference in the cardiac output of Atlantic cod acclimated to either 10 or 0°C measured at the respective acclimation temperature. Still missing from a full understanding of this cardiac compensatory mechanism is the connection between the necessary molecular-and protein-level changes induced by cold acclimation and the resultant changes in whole heart function.…”

“…Previous studies utilizing in situ cardiac preparations for studies of teleost fish set input pressure close to 0 for baseline conditions (Graham and Farrell, 1989;Farrell et al, 1996;Mendonça et al, 2007). It should be noted that systolic pressure (output pressure) was not set at a constant as in previous in situ work (Graham and Farrell, 1990;Farrell et al, 1996;Lurman et al, 2012), rather the diastolic and systolic pressures were measured inside the ventricle after changes in balloon volumes. The systolic pressures that were measured at baseline conditions were within the range of those that were used in previous in situ studies that controlled output pressures.…”

“…For example, in rainbow trout tested at 15°C, Graham and Farrell (Graham and Farrell, 1990) started experiments by setting output pressure to 29 mmHg; and in Farrell et al (Farrell et al, 1996) output pressure was regulated between 30 and 60 mmHg. Moreover, the systolic pressures measured were similar to those used in studies on other fish species including the Atlantic cod, in which output pressures were set to between 15 and 60 mmHg during testing (Lurman et al, 2012).…”

Cold-acclimation leads to differential regulation of the steelhead trout (Oncorhynchus mykiss) coronary microcirculation

“…Moreover, given that temperature has a profound effect on numerous aspects of cardiac metabolic demand and perfusion (35), and that no data exist on the effects of temperature on q Cor or resistance, these experiments were performed at several acclimation temperatures (1, 5, and 10°C). These temperatures were chosen because we know very little about the cardiovascular physiology of nonpolar species at cold temperatures, and this is presently a focus in our laboratory (e.g., 59, Costa IASF, Hein TW, Secombes CJ, and Gamperl AK; unpublished observations).…”