title: Modification of liver mitochondrial lipids and of adenine nucleotide translocase and oxidative phosphorylation by cold adaptation.
abstract: The decrease in respiration rate following thyroidectomy is preceded by changes in the lipid composition of the mitochondrial membrane (Hoch, F.L., Subramanian, C., Dhopeshwarkar, G.A. and Mead, J.F. (1981) Lipids 16, 328-334) and in concert, changes in the kinetic parameters of the adenine nucleotide translocase (Mak, I.T., Shrago, E. and Elson, C.E. (1981) Fed. Proc. 40, 398). To demonstrate that physiological adaptation also involves this sequence of events, rats were housed at 8 degrees C for 3-4 weeks. Cold adaptation resulted in a modest (5%) increase in the unsaturation index for the mitochondrial fatty acids comprised of a significant increase in arachidonic acid and a reciprocal decrease in linoleic acid. Phospholipid analysis indicated that cold adaptation increased the mitochondrial phosphatidylethanolamine and reciprocally decreased the phosphatidylcholine content. Concomitantly, cold adaptation resulted in 25-30% increases in rat liver mitochondrial respiratory activities without changing the respiratory control or ADP/O ratios. The kinetic parameters of the adenine nucleotide translocase were determined by the back-exchange method (Pfaff, E. and Klingenberg, M. (1968) Eur. J. Biochem. 6, 66-79). At 0-4 and 10 degrees C, the Vmax and Km of the cold-adapted rat liver adenine nucleotide translocase were not distinguishable from the control values. The Ki values determined by Dixon plot studies for atractylate and palmitoyl-CoA were also comparable between the two groups. However, at 25 and 37 degrees C, cold-adapted rat liver adenine nucleotide translocase exhibited a 20% increase in Vmax and a 20% decrease in Km for external ADP. The results suggest that one adaption to a cold environment involves hormone-mediated changes in the lipid composition in the mitochondrial membranes which in turn modulate the adenine nucleotide translocase and subsequent respiratory activities.
mesh_terms: D000064:Acclimatization; D000818:Animals; D003080:Cold Temperature; D007425:Intracellular Membranes / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008563:Membrane Lipids / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism*; D000226:Mitochondrial ADP, ATP Translocases / Q000378:metabolism*; D009713:Nucleotidyltransferases / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D008563:Membrane Lipids; D000226:Mitochondrial ADP, ATP Translocases; D009713:Nucleotidyltransferases