the enzyme mass by radioimmunoassay was 1.7 , 4.1 , 7.9 and 13.7 ng/ml culture medium ( or 8.3 , 19.9 , 38.5 and 66.7 ng/mg cell protein ) , respectively , and enzyme activity using an exogenous source of phosphatidylcholine/cholesterol liposomes containing apolipoprotein a-i as substrate was 85 , 170 , 315 , and 402 pmol cholesterol esterified/h per ml culture medium ( or 414 , 828 , 1534 and 1957 pmol cholesterol esterified/h per mg cell protein ) for 6 , 12 , 24 , and 48 h of culture , respectively .
C0008377
cholesterol
C0008387
cholesterol