EXPRESSION OF LIPOPROTEIN-LIPASE DURING DIFFERENTIATION OF CULTURED L6 MUSCLE-CELLS

The presence of lipoprotein lipase (LPL) in L6 muscle cells is equivocal. Analysis of a 21-day time course indicates that these cells express both LPL activity and mRNA. Lipase activity peaked at 4 days after plating and decreased to a nadir at day 21 after plating. Characterization of lipase activity at 4 and 19 days after plating, corresponding to myoblasts and myotubes, respectively, indicated that most of the enzyme activity had the properties of LPL, including an alkaline pH optimum, a serum requirement, and inhibition by NaCl. LPL mRNA expression peaked at 7 days after plating and fell slightly (24%) at day 21. The primary LPL mRNA species in these cells is 3.7 kb in length. Lipase activity and LPL mRNA were highly correlated during the time course (r = +0.82), suggesting transcriptional regulation of the enzyme. These data clearly demonstrate that L6 cells express LPL during differentiation.