Acute and chronic effects of temperature on ion homeostasis and energy metabolism in teleost hepatocytes

KRUMSCHNABEL G, BIASI C, SCHWARZBAUM PJ, WIESER W.

JOURNAL OF COMPARATIVE PHYSIOLOGY B-BIOCHEMICAL SYSTEMIC AND ENVIRONMENTAL PHYSIOLOGY

SPRINGER HEIDELBERG

Año: 1997 p. 280 - 286

0174-1578

Short- and long-term effects of temperature onion ¯ux and energy turnover were studied in hepatocytesfrom thermally acclimated trout and roach. In trouthepatocytes K+ efflux was insensitive towards acute exposureto low temperature but was downregulated duringcold acclimation of the ®sh so as to balance theuncompensated decreased K+(Rb+) uptake of the cells.In contrast, both K+(Rb+) uptake and K+ efflux ofroach hepatocytes were temperature sensitive in theshort term. These acute effects, however, were offsetduring cold acclimation by a near perfect compensationof both ¯uxes leading to re-establishment of ion ¯uxhomeostasis at the original level. Our ®ndings, based ona new method permitting the simultaneous monitoringof K+ efflux and uptake in the same cell population,provide experimental veri®cation of two of the threepossible strategies, recently discussed by Cossins et al.(1995), by which the ionic steady state of ®sh cells mayadjust to acute and chronic temperature change. Bycomparing hepatocytes from two groups of trout, onekept on a maintenance diet (ration I), the other fed adlibitum (ration II), we discovered striking effects of nutritionalstate on the absolute levels as well as on thetemperature relationships of K+ uptake and proteinsynthetic activity. Both of these functions in the hepatocytesincreased in the ration II fed as compared to theration I fed trouts, but the increase of protein syntheticactivity was greater and more uniform at the three experimentaltemperatures than that of K+ uptake.Moreover, protein synthetic activity proved to be considerablymore temperature sensitive than K+ uptakeand, in contrast to the latter, showed a compensatoryresponse after cold acclimation.