PT  - JOURNAL ARTICLE
AU  - BAILEY, JOHN R.
AU  - DRIEDZIC, WILLIAM R.
TI  - ENHANCED MAXIMUM FREQUENCY AND FORCE DEVELOPMENT OF FISH HEARTS FOLLOWING TEMPERATURE ACCLIMATION
DP  - 1990 Mar 01
TA  - Journal of Experimental Biology
PG  - 239--254
VI  - 149
IP  - 1
4099  - http://jeb.biologists.org/content/149/1/239.short
4100  - http://jeb.biologists.org/content/149/1/239.full
SO  - J. Exp. Biol.1990 Mar 01; 149
AB  - Inotropic and chronotropic responsiveness of yellow perch {Perca flavescens Mitchill) and smallmouth bass (Micropterus dolomieui Lacépède) hearts, following low temperature acclimation, was assessed with ventricle strips mounted for isometric force recording. Animals were acclimated to 20° and 5°C, and the performance of ventricle strips from both acclimation temperatures was monitored at 20° and 5°CVentricle strips from yellow perch acclimated to 20°C showed an increase in resting tension when tested at 5°C in the presence of high levels of extracellular calcium. An increase in resting tension did not occur in preparations from 5°Cacclimated fish tested at 5°C. This suggests failure of intracellular calcium regulation which may be ameliorated following an acclimation periodVentricle strips were subjected to a force-frequency challenge over the range of 12–48 contractions min−1 at lmmoll−1 andSmmoll−1 extracellular calcium. Time to 50% relaxation of ventricle strips tested at 5°C was significantly lower for hearts from perch acclimated at 5°C than from those acclimated at 20°C. This was associated with an ability to maintain function at higher pacing rates. Similar trends were exhibited by hearts from smallmouth bass. As calcium extrusion is a prime determinant of relaxation time, these findings further suggest an enhancement in calcium handling capabilities following acclimation to low temperatureVentricle strips from both species acclimated to 20°C and tested at 20°C were able to maintain force development to the highest contraction frequencies. Hearts from specimens acclimated to 5°C and tested at 20°C showed a negative force-frequency relationship at low extracellular calcium levels. In yellow perch, this effect was minimized by an increase in calcium availability. This is considered to be a potential mechanism by which animals acclimated to low temperature could make transient excursions into warm water