FATTY-ACIDS REDUCE HEPARIN-RELEASABLE LPL ACTIVITY IN CULTURED CARDIOMYOCYTES FROM RAT-HEART

Varying glucose and fatty acid (FA) concentrations in the medium of cu ltured cardiomyocytes from adult rat hearts were tested for effects on lipoprotein lipase (LPL) activity. Glucose (5.5, 11, and 25 mM in the culture medium for 18-22 h) had no effect on either heparin-releasabl e LPL (HR-LPL) or on cellular LPL (C-LPL) activities. When cardiomyocy tes were cultured overnight with 60 mu M oleate, HR-LPL activity was r educed to 20% of control, with no change in C-LPL activity or total C- LPL mass. Similar results (HR-LPL and C-LPL activities) were obtained with 60 mu M concentrations of palmitate and myristate; linoleate and eicosapentaenoate did reduce C-LPL activity, but the decrease in HR-LP L activity was much greater. Oxfenicine, an FA oxidation inhibitor, di d not alter the inhibitory effect of 60 mu M oleate on HR-LPL. Short-t erm incubations (1 and 3 h) of cultured cardiomyocytes with 60 mu M ol eate did not displace LPL into the medium. Immunodetectable LPL on the cell surface of oleate-treated cultured cardiomyocytes was increased compared with control cells, but heparin treatment released the same a mount of LPL mass that had reduced catalytic activity.