Esterification of cholesterol in fish plasma: studies on the cholesterol esterifying enzyme in plasma of char (Salmo alpinus L.).

1. Plasma of sea char (Salmo alpinus L.) has the ability to esterify cholesterol in vitro. Heat inactivation of the plasma totally inhibited the esterification. 2. Arrhenius plot of the esterification of [3H]cholesterol was linear in the temperature range 5-35 degrees C. 3. Cholesterol esterification in sea char plasma could not be reversibly inhibited by sulphydryl-blocking agents. Total equilibration of the added [3H]cholesterol and the endogenous cholesterol could therefore not be obtained. 4. Comparison of esterification of endogenous and labelled cholesterol revealed that the isotopic method was valid only in qualitative measurements.