Secretion of lipoprotein lipase by macrophages in culture

Cultured macrophages were shown to synthesize and constitutively secrete a triglyceride lipase identified as lipoprotein lipase on the basis of the following criteria: 1) it required apolipoprotein C-II for optimal activity; 2) it exhibited maximal activity at pH 8.2; 3) it was inhibited by 1 M NaCl; 4) it bound tightly to a heparin-Sepharose affinity gel and was eluted with buffer containing 1.5 M NaCl; and 5) the quantity of enzyme released from macrophages was enhanced by heparin. Cycloheximide treatment of macrophage cultures blocked the spontaneous secretion of lipoprotein lipase. Macrophage secretion of lipoprotein lipase may be relevant to the role of this cell in atherogenesis.