INVESTIGATIONS INTO HYPERLIPIDEMIA AND ITS POSSIBLE ...

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the results of these initial studies are hard to interpret today mainly because of the
different terminology and classification schemes used. Nevertheless, some basic
information can be derived from those initial studies. For example, these studies showed
that the majority of lipoproteins found in dogs (~75%) have a very low flotation rate (-
3S) and thus would be classified as HDL molecules today (most likely HDL 2 and
HDL 3 ). 1-5 Lipoproteins with higher flotation rates (-6S and -27S) were found to represent
between 1% and 10% of the total lipoproteins of canine serum, and likely included LDL,
VLDL, and chylomicron molecules. 1-5
Subsequent studies in the 1970s by Solyom and colleagues 6,7 and Mahley and
colleagues 8-10 provided additional information on lipoproteins in fasted healthy dogs, and
showed that canine plasma lipoproteins consisted primarily of HDL 2 , with much lower
concentrations of HDL 1 and LDL. Chylomicrons and VLDLs were found only in dogs
that were fasted for less than 12 hours. These researchers also determined the protein and
lipid distribution of canine lipoproteins. They reported that 85% of total plasma
cholesterol was carried by HDL 2 , and 50% of plasma triglyceride was carried by VLDL.
The above mentioned studies were also the first ones to describe in more detail some of
the apoproteins found in each lipoprotein fraction. In their studies, both Solyom and
colleagues and Mahley and colleagues used ultracentrifugation combined with
electrophoresis for lipoprotein fractionation and characterization. In addition,
immunohistochemical studies were performed to describe the apoproteins found in each
lipoprotein fraction.