Journal of Lipid Research, Vol. 2, 161-168, April 1961
Copyright © 1961 by Lipid Research, Inc.

Recombination with lipids of the lipid-free protein from canine serum (d 1.063-1.21, ₁) lipoprotein

Angelo Scanu and Irvine H. Page

Research Division, Cleveland Clinic Foundation and the Frank E. Bunts Educational Institute, Cleveland 6, Ohio

The protein (P), prepared by delipidation of canine serum ₁-lipoprotein (LP), when labeled with I¹³¹ and injected into dogs, was metabolized at the same rate as native LP, labeled in the protein moiety with I¹³¹. When P-I¹³¹ was added to serum or injected into dogs, the radio-activity promptly appeared only in the LP fraction, indicating a preferential interaction of the labeled protein with its own lipoprotein class. The nature of this interaction was not established. Mixing of P-I¹³¹ with the low density lipoprotein class (ßbeta;LP), in absence of serum, yielded two radioactive fractions, floating at d 1.063 and d 1.21. These two fractions had electrophoretic mobility similar to radioiodinated native ßbeta;LP and LP. In the absence of serum, P-I¹³¹ reacted also with chylomicrons from serum or chyle. When the radioactive chylomicrons thus formed were injected into dogs, their disappearance from circulation paralleled that of an injected Lipomul (artificial triglyceride emulsion)-LP-I¹³¹ complex. In both instances the disappearance of triglycerides was accompanied by appearance of radioactivity in the LP fraction of plasma. When Lipomul was given intravenously to dogs injected with LP-I¹³¹, it combined with a small amount of this labeled lipoprotein. The possible participation of LP in the metabolism of triglycerides is briefly discussed.

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