Lipid dynamics and protein-lipid interactions in rat colonic epithelial cell basolateral membranes

Lipid dynamics and lipid-protein interactions were examined in basolateral membranes prepared from rat proximal and distal colonic epithelial cells. The results demonstrate that: (1) these membranes have a high lipid fluidity, as assessed by steady-state fluorescence polarization studies using seven fluorescent probes; (2) lipid compositional differences exist between these membranes but their fluidity is similar; (3) fluorescence polarization studies, using diphenylhexatriene (DPH), detect a thermotropic transition at 22-23 degrees C in each membrane; (4) several membrane protein activities, including adenylate cyclase and sodium-potassium dependent adenosine triphosphatase ((Na+ + K+)-ATPase) appear to be functionally dependent on the physical state of the proximal basolateral membrane's lipid.