| Popis: |
SUMMARY The protein ( aP), prepared by delipidation of canine serum al-lipoprotein (aLP), when labeled with 1131 and injected into dogs, waa metabolized at the same rate as native aLP, labeled in the protein moiety with 1131. When aP-P waa added to serum or injected into dogs, the radioactivity promptly appeared only in the aLP fraction, indicating a preferential interaction of the labeled protein with ita own lipoprotein class. The nature of this interaction was not established. Mixing of aP-1131 with the low density lipoprotein class (PLP), 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 BLP and aLP. In the absence of serum, aP-P1 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 em~lsion)-aLP-I~3~ complex. In both instances the disappearance of triglycerides was accompanied by appearance of radioactivity in the aLP fraction of plasma. When Lipomul was given intravenously to dogs injected with aLP-113', it combined with a small amount of this labeled lipoprotein. The possible participation of aLP in the metabolism of triglycerides is briefly diecussed. Studies from this laboratory have shown that the high density d 1.063-1.21 lipoprotein of human serum can be freed of practically all its lipids to yield a protein, apparently undenatured and identical from the immunochemical standpoint, with the native lipoprotein (1, 2). Further, in vitro experiments have shown that this lipid-free protein has high avidity for lipids and, under suitable conditions, combines with them to reconstitsUte the original protein-lipid complex (3). The studies reported below deal with the in vitro and in z$/o recombining capacity for lipids of the lipid-free protein from d 1.063-1.21 lipoprotein of canine serum. |
