Papers by Lic. Enrique Orozco
Universidad Colegio Mayor Nuestra Senora Del Rosario Universidad Del Rosario Edocur Repositorio Institucional Disponible En Http Repository Urosario Edu Co, Feb 1, 2012
La Revista del Rosario es la publicacion institucional universitaria mas antigua del pais. Desde ... more La Revista del Rosario es la publicacion institucional universitaria mas antigua del pais. Desde 1905, sin interrupciones, sus paginas reflejan los personajes, los temas y los debates centrales que atanen a la comunidad rosarista.
Human total HDL (high-density lipoprotein), HDL2 and HDL3 were labelled in vitro by incubation wi... more Human total HDL (high-density lipoprotein), HDL2 and HDL3 were labelled in vitro by incubation with lipoproteindeficient serum (LPDS) which contained either [3H]cholesteryl oleate or [14C]cholesterol under different conditions. The lipoproteins were then subfractionated by heparin-Sepharose column chromatography, and three subfractions (A, B and C) were successively eluted from each preparation of HDL, HDL2 and HDL3. When the labelling was done at 37°C for 17 h, the subfractions were homogeneously labelled with [3H]cholesteryl oleate. However, when it was performed for only 30 min at 4°C, the subfractions showed marked differences in the 3H specific radioactivity, which was much higher in the C fractions than in the others. 2. 3H-labelled HDL2 and HDL3 subfractions behaved differently under the precipitant action of heparin-Mn2+; fraction C (the richest in apolipoprotein E) produced the largest amount of radioactive and chemical precipitate. More 3H radioactivity, but not the cholesterol, was precipitated from HDL2 or HDL3 by the reagent, demonstrating that 3H-labelled HDL2 and HDL3 behave like their fraction C, which becomes labelled to the highest specific radioactivity despite having the smallest mass. 3. The incubation of 3H-labelled HDL subfractions with human LPDS and very-low-density lipoprotein (VLDL) at 37°C increased the quantity of 3H radioactivity that was precipitated, in proportion to the amount of VLDL present in the media. These changes were attributable to the action of cholesterol ester transfer protein, since they did not occur at 4°C or when human LPDS was replaced with rat LPDS. 4. Kinetics of the transfer of HDL [3H]cholesteryl oleate to VLDL showed a greater apparent Vmax for fractions A than for fractions B from either HDL2 or HDL3, whereas the apparent Km values were very similar, which suggest that this transfer process is influenced by the apoprotein composition of the donor lipoprotein. Labelling with 13Hlcholesteryl oleate Labelling of the HDL preparations with [3H]cholesteryl oleate was by the method of Roberts et al. [8]. In brief, approx. 25 ,uCi of [1,2,6,7-3H]cholesteryl oleate (65.8-82.9 Ci/mmol; New England Nuclear, Bad Homburg, Germany) in 0.1 ml of acetone was dripped over 15 ml of human LPDS with stirring, and the acetone was evaporated under a N2 stream. A given volume of 3H-containing LPDS was mixed with an equal volume of total Vol. 270 Abbreviations used: VLDL, very-low-density lipoproteins; LDL, low-density lipoproteins; HDL, high-density lipoproteins; apo, apoprotein; LPDS, lipoprotein-deficient serum; CETP, cholesteryl ester transfer protein; LCAT, lecithin: cholesterol acyltransferase.
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Papers by Lic. Enrique Orozco