SEASONAL-VARIATIONS OF PHYSICAL AND BIOCHEMICAL MEMBRANE-PROPERTIES IN TROUT ERYTHROCYTES (SALMO-IRIDEUS)

Erythrocyte membranes from Salmo irideus trout were analysed month by month, focusing on (1) Na+,K+-ATPase activity; (2) cholesterol content ; (3) generalised polarization of laurdan, reflecting membrane lipid p olarity and (4) 1,6-diphenyl-1,3,5-hexatriene steady-state fluorescenc e anisotropy, related to ''membrane fluidity.'' properties (2) and (3) showed clear maxima during winter, property (1) during summer, wherea s property (4) was not much influenced by season. Clearly, Na+,K+-ATPa se activity of trout erythrocytes is influenced by the physical state of membrane lipids on a monthly scale.