Use of fluorescence polarization to monitor intracellular membrane changes during temperature acclimation. Correlation with lipid compositional and ultrastructural changes

Abstract

Fluorescence polarization of 1,6-diphenylhexatreine (DPH) was used to study the effects of temperature acclimation on Tetrahymena membranes. The physical properties of membrane lipids were highly dependent on cellular growth temperature. DPH polarization in lipids from 3 different membrane fractions correlated well with earlier freeze-fracture and electron spin resonance observations showing that membrane fluidity progressively decreased in the order microsomes > pellicles > cilia throughout a wide range of growth temperatures. Changes in membrane lipid fluidity following a shift from high to low growth temperatures proceeded rapidly in the microsomes, whereas there was a pronounced lag in changes of peripheral cell membrane lipids. Adaptive changes in membrane fluidity probably proceeded via lipid modifications in the endoplasmic reticulum, followed by dissemination of lipid components to other cell membranes. The rapid changes in polarization observed in the microsomal lipids following a temperature shift corresponded closely with time-dependent alterations in lipid fatty acid composition and freeze-fracture patterns of membrane particle distribution, suggesting that, in the endoplasmic reticulum, lipid phase separation was the primary cause of membrane particle rearrangements.