The differences of serum lipid and lipoprotein (LP

profiles of animals susceptible （rabbit） and nonsusceptible （Beijing duck） to atherosclerosis as well as the distribution of apolipo- protein （apo） A-I and its catabolism in vivo were studied.Eight items

i.e.total cholesterol （TC）

high density lipoprotein （HDL） cholesterol

triglyceride

percentage of a-LP and β-LP

β-LP concentration

lecithin cholesterol acyl transferase （LCAT）

and agarose and polyacryla- mide gel electrophoresis of both species were assayed before and after feeding a high fat

high cholesterol diet.Results indicate that the exogenous cholesterol consumed by Beijing ducks was carried and transported by HDL

while that in rabbits was transported by low density lipoprotein （LDL）.The biological half lives of apo A-I in serum and in HDL were 41.11±2.4 and 42.8±1.7 h respectively.and its distribution in different organs was in the order of liver>kidney>spleen>lung>heart>intestine>muscles>aorta.These results show that the liver is the major organ for metabolizing HDL apo A-I.and the kidney is also important.The results also imply that in Beijing ducks the cholesterol carried by HDL may be catabolized through apo A-I receptors in the liver and kidney.The differences in cholesterol binding and in lipoprotein and apolipoprotein metabolism of the two species provide important clues for the elucidation of the pathogenesis of atherosclerosis.