title: Changes in the composition and fluidity of membranes in obese (ob/ob) mice: a study of hepatic microsomal NADPH-cytochrome P450 oxidoreductase activity.
abstract: The characteristics of microsomal membrane lipids in obese (ob/ob) mice have been probed by studies on the microsomal enzyme NADPH-cytochrome P450 oxidoreductase and by investigation of their fluidity using the fluorescence probe 1,6 diphenylhexatriene. Arrhenius plots of NADPH-cytochrome P450 oxidoreductase activity were biphasic with the break temperature in obese mice reduced from 9.5 to 6.5 degrees C. The activation energy of NADPH-cytochrome P450 oxidoreductase was increased in obese microsomes below the Arrhenius breakpoint. Normalising the body temperature of ob/ob mice did not rectify the Arrhenius plot of NADPH-cytochrome P450 oxidoreductase activity of ob/ob mice. DPH fluorescence polarisation indicated that the gross phospholipids from ob/ob mouse microsomes were more fluid than those from lean mice. Phosphatidylethanolamine (PE) of ob/ob microsomes contains a higher proportion of unsaturated fatty acids resulting mainly from an increase in 22:6 and a fall in 16:0. Phosphatidyl choline (PC) of ob/ob microsomes contains an increased proportion of saturated fatty acids. Phospholipid vesicles of obese microsomal PE were more fluid and obese microsomal PC less fluid than the equivalent phospholipids from lean mice microsomes. The changes in Arrhenius plots of NADPH-cytochrome P450 oxidoreductase activity of obese microsomes are interpreted in relation to the reported phospholipid changes.
mesh_terms: D000818:Animals; D001831:Body Temperature; D001833:Body Temperature Regulation; D004161:Diphenylhexatriene; D008297:Male; D008560:Membrane Fluidity; D051379:Mice; D008820:Mice, Obese / Q000502:physiology*; D008862:Microsomes, Liver / Q000201:enzymology*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000032:analysis; D010714:Phosphatidylethanolamines / Q000032:analysis; D010743:Phospholipids / Q000032:analysis; D013696:Temperature
chemical_list: D010713:Phosphatidylcholines; D010714:Phosphatidylethanolamines; D010743:Phospholipids; D004161:Diphenylhexatriene; D009251:NADPH-Ferrihemoprotein Reductase