Direct adaptation of cells to temperature: Membrane fluidity of goldfish cells cultured in vitro at different temperatures

1. 1. Membrane fluidity (reciprocal of structural order) of crude membrane preparations of CAF cells from goldfish fin cultured at different temperatures was measured by the steady-state fluorescence polarization technique at 10–30°C using l,6-diphenyl-l,3,5-hexatriene (DPH) as the fluorophore. 2. 2. The polarization value was statistically significantly higher (the fluidity was lower) in preparations from log phase cells cultured at 36°C for more than 2 years than in those cultured at 24°C, showing 52% compensation. 3. 3. The cells cultured at 14°C for 3–6 months showed lower polarization values (higher fluidity) corresponding to 34% compensation, although those cultured at the same temperature for more than 2 years showed only 19% compensation (statistically not significant). 4. 4. The extent of partial compensations observed in cells cultured in vitro is comparable to that reported in tissues of thermally acclimated fishes and frogs, suggesting that the homeoviscous adaptation of cell membranes of poikilothermic vertebrates exemplifies the “direct adaptation” (Precht, 1973) where information on environmental temperature need not be mediated by nervous or hormonal regulatory systems of the whole animal.