A rapid method for lecithin:cholesterol acyltransferase estimation in human serum.

All the described procedures for lecithin:cholesterol acyltransferase (LCAT) determination in the plasma have raised criticisms: Lack of sensitivity for methods using colorimetric determination of unesterified cholesterol or phosphatidyl-choline in plasma before and after incubation at 37 degrees C. Incomplete isotopic equilibrium of the free cholesterol substrate between the different lipoproteins in radioassay procedures. Gas-liquid chromatography methods cannot be used when LCAT activity is low. A new method, easier, more sensitive and accurate has been developed in our laboratory:plasma samples are delipoproteinized by coprecipitation with Intralipid, dextran sulphate, and calcium chloride. Cholesterol esterification is assayed by a short incubation (30 min) of 100 microliter delipoproteinized plasma and a 30 microliter of 3H-cholesterol-labelled substrate. About 15% of cholesterol is esterified in these conditions in 30 min (35 +/- 7 micromole/h/l). The LCAT reaction is linear for about one hour.