Effects of temperature on the (Na+ + K+)-ATPase and oxygen consumption in hepatocytes of two species of freshwater fish, roach (Rutilus rutilus) and brook Char (Salvelinus fontinalis)

SCHWARZBAUM PJ,NIEDERSTAETTER H, WIESER W

PHYSIOLOGICAL ZOOLOGY

Elsevier

Año: 1992 p. 699 - 711

0031-935X

Effects of temperature on the (Na+ + K+)-ATPase were studied in isolated hepato- cytes of two species offreshwater fish acclimated to different temperatures. Bind- ing of 3H+-ouabain to bhepatocytes was used to determine the density of (Na+ + K+)-ATPase, and oxygen consumption was measured to estimate the cost of cation pumping. Intracellular sodium concentration was manipulated by incu- bating hepatocytes at 200C or 00-4'C before the measurement of oxygen con- sumption. In hepatocytes of Rutilus rutilus, the maximal number of ouabain binding sites per 106 cells (Bmax) was 1.86 times higher in the 50 C- acclimated than in the 200 C-acclimated group. The equilibrium dissociation constants (Kd's) in both acclimation groups were not statistically different. In Salvelinus fontinalis, Bmax and Kd values did not change with temperature acclimation. Ouabain-sensitive oxygen consumption (OS) in hepatocytes of R. rutilus was 1.60-1. 73 times higher in the cold- than in the warm-acclimated group. In S. fon- tinalis, acclimation temperature did not affect OS. On the other hand, cold prein- cubation of hepatocytes significantly increased OS in both acclimation groups and species. Results are discussed with regard to species-specific differences in the adaptation to temperature change at the cellular level, the main point being that in response to cold-acclimation R. rutilus adjusts the activity of the (Na+ + K+)- ATPase in a compensatory fashion, whereas S. fontinalis modulates passive ion leakage.