The Effect of Temperature Acclimation and Adrenaline on the Performance of a Perfused Trout Heart

Abstract

Cardiac performance was examined with in situ perfused trout hearts at two acclimation temperatures, 5 C and 15 C. In series I, adrenaline-free perfusion and a cumulative dose response up to 1 μgmol adrenaline · L⁻¹ was examined. In series II, tonic adrenergic stimulation (5 nmol · L⁻¹) and a cumulative dose response up to 50 nmol · L⁻¹ was examined Tonic adrenergic stimulation was important for chronotropic and inotropic stability, especially at5 C. Heart rate and maximum cardiac output were significantly higher at 15 C than at5 C. Maximum stroke volume at 5 C was the same as or greater than the maximum stroke volume at 15 C Adrenergic stimulation produced quantitatively different positive chronotropic and inotropic effects at both temperatures and partially compensated for the direct efect of temperature; the chronic Q10 values for heart rate and maximum cardiac output were 1.30-1.40. Trout acclimated to 5 C had a relatively larger ventricle mass, which permitted a higher absolute stroke work at 5 C than at 15 C