Specific modification of hepatic triglyceride lipase activity by ultracentrifugally separated serum lipoprotein fractions.

Hepatic triglyceride lipase (H-TGL) obtained from postheparin plasma is first stimulated and than progressively inhibited by addition of an increasing amount of serum. To solve the mechanism of this modification, serum fractions isolated by ultracentrifugation were added to the assay mixture and their effects on H-TGL activity were determined. We demonstrated that the addition of the d=1.21 bottom fraction together with HDL almost fully reproduces the effect of the whole serum.