Studies on Lipoprotein Lipase
Lipoprotein lipase (LPL) activity in cultured mesenchymal cells derived from new-born rat heart, increases during the final week after plating and then plateaus [1, 2]. Expression of LPL requires the presence of 20% serum and activity decreases markedly in serum-poor medium [3,4], Basic fibroblast growth factor (bFGF) plays an important role in cell proliferation and presently we have inquired whether it may replace serum in our system and whether it will affect LPL activity also in the presence of serum. In the experiments shown in Table I, it is evident that addition of 200 ng FGF/ml to cultures incubated with only 0.5% serum prevented the fall in LPL activity observed in nonsupplemented controls kept for 48 h in the presence of 0.5% serum. When FGF was added to cultures in the presence of 20% serum its effect varied, depending on the time of addition. When addition of FGF was started on day 3 after plating, and LPL activity was determined 3 days later, LPL activity in the treated dishes was 3 times that of untreated controls (Table II). However, if the growth factor was added to cells in which maximal activity was seen (11 days after plating), there was no further increase in LPL activity. The effect of LPL was at the transcriptional level and resulted in an almost 3-fold increase in LPL mRNA as well as in enzyme mass.
KeywordsLipase Stein Kato Cholera Dibutyryl
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