Journal of Lipid Research, Vol 28, 900-912, Copyright © 1987 by Lipid Research, Inc.
Subfractionation of 1.006-1.063 g/ml components of badger plasma lipoproteins by using heparin-Sepharose affinity chromatography: relevance to the endocrine regulation of lipoprotein metabolism
PM Laplaud, L Beaubatie, SC Rall and D Maurel
Laboratorie de Biochimie Medicale, Faculte de Medecine et de Pharmacie, Limoges, France.
Badger plasma lipoproteins with density 1.006-1.063 g/ml have been
subfractionated by means of affinity chromatography on a heparin- Sepharose
column, using a modification of the method reported by Weisgraber and
Mahley (1980. J. Lipid Res. 21: 316-325). These experiments have provided
evidence for the presence of three lipoprotein subfractions hereinafter
termed fractions I, II, and III. Fraction I was cholesteryl ester- and
phospholipid-rich (ca. 35% and 30% of lipoprotein mass, respectively), and
contained apoA-I as its prominent apolipoprotein constituent. In contrast,
triglyceride-rich fractions II and III both exhibited a complex
apolipoprotein pattern, including apoB-100, apoA-I, and apoE whose amino
acid composition and NH2-terminal sequence in the badger are reported.
However, fraction III appeared markedly enriched in apoE when compared to
fraction II. On polyacrylamide gel electrophoresis, fraction I presented as
a spectrum of particles with diameters in the 140-190 A range. In contrast,
fraction II migrated as a single band with a diameter of approximately 200
A, and fraction III presented as a single band or a doublet with a diameter
of 195-200 A. The respective plasma concentrations and chemical
compositions of the three chromatographic fractions were determined at four
different dates of the year (i.e., April, August, November, and January),
each of which corresponded to a different endocrine status in the badger.
Thus hypothyroidism appeared to be associated with an increase in the
concentration of fraction I, while the lowering in summer of the plasma
level of testosterone correlated well with an increase in the concentration
of fraction II. At the same time, the respective proportions of hydrophobic
lipids in this latter material modified with an increase of triglycerides.
Finally, both the apolipoprotein pattern of fraction III, and the
chronologic profile of the successive variations of its concentration,
suggest that it could represent a metabolic precursor of fraction II. These
results suggest that the respective metabolism of the lipoproteins
constituting the three chromatographic fractions could be under control by
thyroid and testis secretions, operating via a complex combined regulation
of the activities of the enzymes and receptors involved in these metabolic
processes.
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