Distribution of oleoyl-estrone in rat plasma lipoproteins

Pooled adult normal rat plasma was used for the separation of lipoprotein f ractions: VLDL, LDL and HDL, from which a total lipids extract was obtained . The presence of fragments with the MW of estrone and oleoyl-estrone in th e lipoprotein fractions was analyzed by HPLC-MS. The results show that oleo yl-estrone is the major estrone component in lipoproteins; this molecular s pecies was present in all three lipoprotein lipid extracts. The lipoprotein fractions were used for the analysis of protein and lipid classes: triacyl glycerols, total and esterified cholesterol and phospholipids as well as ac yl-estrone. About half of the total acyl-estrone was in the HDL fraction an d only about 10% in the VLDL fraction. HDLs contained about one molecule in 50 particles, LDLs one molecule per particle and VLDLs 15 molecules per pa rticle, i.e. given their size, the larger lipoproteins contained more oleoy l-estrone than the HDLs. The distribution of this hormone suggests that ole oyl-estrone is lost with other lipids as the lipoproteins shrink. The resul ts presented show that oleoyl-estrone is a molecule found naturally in rat lipoproteins in low concentrations - the lowest in HDLs - that are consiste nt with its postulated role in the control of body weight.