Rabbits as a Model for the Study of Hyperlipoproteinemia and Atherosclerosis

Abstract

Lipoproteins of normal and cholesteremic plasma were compared in New Zealand White (hyperresponder) and Dutch Belt (hyporesponder) rabbits. Three major differences were observed between the strains: (1) New Zealand White rabbits developed much higher plasma levels of very low, intermediate, and low density lipoproteins after cholesterol feeding; (2) Dutch Belt rabbits, normal and cholesteremic, had higher ratios of the more dense high density lipoproteins HDL₃ (d 1.125−1.20 g/ml) to the less dense HDL₂ (d 1.081−1.125 g/ml); (3) cholesteremic Dutch Belt rabbits had higher plasma levels of the more dense HDL₃ subfraction than did cholesteremic New Zealand White rabbits.

Cholesteremic very low density lipoproteins of both strains are large particles of beta electrophoretic mobility that are rich in cholesteryl esters and an arginine-rich apolipoprotein(s). The intermediate and low density lipoprotein fractions were similarly altered in composition, although the proportion of arginine-rich protein to total protein was less than in the very low density fraction. Although the high density lipoproteins were greatly decreased in concentration in cholesteremic plasma, no major changes in their apolipoproteins were seen in either strain of rabbits. The major high density apolipoprotein of rabbits occurs in two electrophoretically separable forms and is similar to human apo A-I. Six minor apolipoproteins were isolated from the high density lipoproteins; some of these occur also in other density fractions.

Erythrocyte membranes of both strains of rabbits before and after cholesteremia were quantitatively similar in their Na⁺-K⁺-ATPase, Mg⁺⁺-ATPase, and Ca⁺⁺-ATPase activities.