Evidence for in Vivo Activity of Postheparin Plasma Lecithinase in Man ∗

Abstract

Plasma obtained after intravenous administration of heparin contains enzymatic activity catalyzing the hydrolysis of triglyceride (TG) in vitro. This activity is also apparent in vivo and results in a decrease in total plasma TG, an increase in products of TG hydrolysis, and a shift of the plasma lipoprotein spectrum from very low density to higher density fractions (1). From prior studies it appeared that no change occurred in total plasma cholesterol or phospholipid (1).

Recent studies have shown that postheparin plasma also contains enzymatic activity catalyzing the hydrolysis of the phospholipids phosphatidyl ethanolamine or phosphatidyl choline (lecithin) in vitro (2,3). Hydrolysis occurs at the α’(C-1) fatty acid with the production of β (C-2) lyso derivatives. Results in the present study indicate that lipoprotein lecithin is hydrolyzed in parallel with TG in vivo after intravenous heparin, and thus provide evidence for the in vivo action of postheparin plasma phospholipase in man.

Methods. Blood samples were obtained from 12 normal adult male subjects prior to and again after rapid intravenous administration of 5000 units of heparin.

Plasma cholesterol and T G were analyzed after extraction in chloroform-methanol (2: 1, v: v) by standard AutoAnalyzer techniques(5).