Mitochondrial phosphatidate is converted to triacylglycerol in rat hepatocytes.
Phosphatidate is formed in both the endoplasmic reticulum and the outer mitochondrial membrane in rat liver. To investigate whether the phosphatidate synthesized in mitochondria can be converted to triacylglycerol in vivo, two experimental approaches were employed. (i) [3H]Phosphatidate-labeled mitochondria were enclosed in plasma membrane vesicles and these fused, in the presence of inactivated Sendai virus and calcium ions, to hepatocytes in monolayer culture. The recovery of radioactivity in various cell-associated lipids was measured. (ii) Mitochondrial phosphatidate was labeled with [14C]palmitate in hepatocytes which had been permeabilized with lysophosphatidylcholine and in which the microsomal glycerolphosphate acyltransferase had been inhibited with N-ethylmaleimide. The recovery of radioactivity in various lipids after incubation with particle free supernatant was measured. Evidence was obtained from both these experimental approaches that mitochondrial phosphatidate can be converted to triacylglycerol in rat hepatocytes. The results are discussed in relation to the role of mitochondrial phosphatidate in liver lipid metabolism.
Department of Biochemistry, University of Nottingham Medical School, Queen's Medical Centre, United Kingdom.
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Mangiapane
D000818:Animals; D002463:Cell Membrane Permeability; D008297:Male; D008930:Mitochondria, Liver / Q000378:metabolism*; D010168:Palmitates / Q000378:metabolism; D010711:Phosphatidate Phosphatase / Q000378:metabolism; D010712:Phosphatidic Acids / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014280:Triglycerides / Q000378:metabolism*
D010168:Palmitates; D010712:Phosphatidic Acids; D014280:Triglycerides; D010711:Phosphatidate Phosphatase