Tritium isotope effects in the measurement of the glycerol phosphate and dihydroxyacetone phosphate pathways of glycerolipid biosynthesis in rat liver

摘要: 1. Rat liver slices were employed to study the relative rates of incorporation a mixture [2-3H]- or [1,3-3H]-glycerol and [1-14C]glycerol into lipids. 2. With 0.1mm-glycerol approx. 82% newly synthesized lipid, calculated from 14C incorporation, was present as neutral 13% phosphatidylcholine 5% phosphatidylethanolamine. Increasing glycerol concentration 40mm caused decrease in percentage lipid 59% corresponding increase 36% lipid. 3. The (d.p.m. 2-3H)/(d.p.m. 1-14C) ratio glycerolipid considerably higher than that precursor throughout range experimental conditions. In contrast [1,3-3H]glycerol occurred with little no change 3H/14C ratio. 4. Respiring rat mitochondria found oxidize sn-[2-3H]- sn-[1-14C]-glycerol 3-phosphate resultant remaining sn-glycerol 3-phosphate. This is due 3H isotope effect mitochondrial dehydrogenase (EC 1.1.99.5), which discriminates against sn-[2-3H]glycerol during oxidation. 5. A method described for simultaneous determination contributions phosphate dihydroxyacetone pathways biosynthesis slices. involves measurement both after incubation [2-3H]glycerol various times. 6. By using this it shown 40–50% incorporated by proceeded via pathway 50–60% phosphate.