[The rate of elimination of homologous and heterologous native and modified high density lipoproteins from rabbit plasma after their intravenous administration].

Rates of catabolism of total fraction of human native high density lipoproteins (HDL) and their subfractions as well as horse and rabbit native and modified HDL were studied after intravenous administration of the HDL into healthy rabbits and the animals with experimental hypercholesterolemia. The following procedures were carried out for production of HDL derivatives: methylation, succination, blocking of Arg residues and of COOH-groups. Rates of catabolism were similar for rabbit and horse total fractions of 125I-HDL, whereas human HDL were catabolized at a slightly higher rates as compared with rabbit lipoproteins. After administration of human total HDL fractions their elimination, estimated by output of alpha-cholesterol (alpha-C), occurred at a higher rate in healthy rabbits as compared with the animals with hypercholesterolemia, whereas output of apoprotein (apo) A-I was similar in both these groups. As HDL are able to exhibit the properties of alpha-C donor in circulation, estimation of apo A-I should be a more reliable index of the HDL content in blood plasma as compared with alpha-C. Chemical derivatives of rabbit HDL were eliminated from circulation of control animals at a rate similar to that of native HDL rate, but exceeding the rate established for succinated HDL. As compared with native HDL all the modified horse HDL were eliminated at the higher rate from the circulation of healthy rabbits. In rabbits with hypercholesterolemia the higher rate of elimination was shown only for succinated and methylated HDL fractions. Succinated HDL were catabolized at the highest rate apparently due to marked negative charge of their molecules. The data obtained suggest that in rabbits HDL are catabolized via pathways which do not involve specific cell receptors.