Effects of thermal acclimation on ventricle size, protein composition, and contractile properties of crucian carp heart

Abstract

1. 1. The aim of the study was to find out how thermal adaptation affects ventricular size, protein composition and functional properties of the contractile machinery of the fish heart. For that purpose crucian carp ( Carassius carassius L.) were acclimated in laboratory to 2° and 22°C for three months. 2. 2. Long-term acclimation to 2° increased the relative ventricular mass by 86% in comparison to fish acclimated to 22°C. 3. 3. The cold-induced cardiac enlargement was associated with a remodelling of protein composition of the ventricular muscle. Total concentration of proteins, including non-collagenous proteins of myocytes and collagenous proteins of extracellular matrix, was increased from 96 to 109 mg g −1 ( P < 0.05) tissue wet weight. The increase was exclusively due to increased concentration of collagenous proteins, since concentration of sarcoplasmic proteins was unchanged and concentration of myofibrillar proteins was reduced. Total hydroxyproline concentration was lower in cold-acclimated animals; the elevated concentration of collagenous proteins is, therefore, not due to collagen but other proteins of the extracellular matrix. Thus, acclimation to cold increases protein concentration of extracellular matrix but reduces protein concentration of the myocytes in crucian carp heart. 4. 4. Effects of caffeine (5mM) on the contractile properties of ventricular myocardium were studied to find out if thermal acclimation alters Ca activation of contraction. Caffeine increase forco of contraction more in the hearts of warm-acclimated (110%) than cold-acclimated fish (40%). Furthermore, relaxation rate and time-course of contraction were differently affected by caffeine in cold- and warm-acclimated fish. These findings suggest that thermal acclimation changes the function of proteins responsible for excitation-contraction coupling.