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 polarity and (4) 1,6-diphenyl-1,3,5-hexatriene steady-state fluorescence anisotropy, related to ''membrane fluidity.'' properties (2) and (3) showed clear maxima during winter, property (1) during summer, whereas property (4) was not much influenced by season. Clearly, Na+,K+-ATPase activity of trout erythrocytes is influenced by the physical state of membrane lipids on a monthly scale.