Hepatic plasma membranes from genetically obese (ob/ob) mice: Studies on fluorescence polarization, phospholipid composition and 5′-nucleotidase activity

Abstract

1. 1. Hepatic plasma membrane lipids of lean (+/?) and obese (ob/ob) mice have been investigated using 1,6-diphenylhexatriene (DPH). 2. 2. Arrhenius plots of DPH fluorescence polarization in membranes showed the breakpoint in obese mice was reduced from 21 to 15°C, whereas the breakpoint of 5′-nucleotidase activity was raised from 23 to 32°C. 3. 3. Arrhenius break temperatures of DPH polarization and 5′-nucleotidase activity responded differently to housing mice at 34°C and triiodothyronine (T 3) treatment. 4. 4. Studies of DPH polarization in liposomes and phospholipid fatty acid composition suggested that differences in sphingomyelin acyl composition determine Arrhenius characteristics of hepatic 5′-nucleotidase in lean and obese mice.