Synthesis and secretion of lipoprotein lipase by human monocyte-derived macrophages

Human monocytes isolated from either defibrinated blood or buffy coat were shown to produce and secrete lipoprotein lipase during culture. The secretion occurred constitutively. Low levels of enzyme activity in the medium from freshly isolated cells increased with time of incubation, and maximal activity was attained after 9 days. The addition of heparin resulted in a substantial increase of enzyme activity in the culture medium. The optimal concentration of heparin was about 2 U/ml. The production of lipoprotein lipase was dependent on the presence of serum in the culture medium, and the optimal supplementation of serum was 25-50%.