Seasonal and temperature effects on steady-state ion distributions of Arctic charr (Salvelinus alpinus) erythrocytes

The effects of thermal history, temperature changes in vitro and seasonal c ycle on the ion contents of Arctic charr erythrocyte in defined medium were studied. The charr was acclimated to three different temperature (2, 8 or 14 degrees C) and the experiments were carried out in winter, spring and su mmer. Erythrocyte membrane preparations from charr and rainbow trout were u sed in order to investigate membrane fluidities after acclimation to differ ent temperatures. Acute temperature changes (in vitro) have no effect on ch arr erythrocytic ion content. In contrast, temperature acclimation changed the intracellular ion composition; cellular water and chloride contents dec reased and potassium content increased with increasing acclimation temperat ure. However, the effect of previous acclimation was seen only in spring. A seasonality of ion contents was evident; there were a reduction in intrace llular sodium content and an elevation in chloride content in summer. Both thermal and seasonal effects were independent of extracellular pH. The memb rane fluidities of charr and trout did not respond to temperature acclimati on, although there were interspecies differences in temperature sensitivity of membrane fluidity (C) 1999 Elsevier Science Inc. All rights reserved.