Effect of taxol on the heparin-induced secretion of lipoprotein lipase from cardiac myocytes.

The heparin-induced secretion of LPL into the incubation medium of cardiac myocytes occurred in two phases: a rapid release (5-10 min), followed by a slower rate of release (10-60 min). Reducing the incubation temperature from 37 degrees C to 23 degrees C inhibited the slow phase of secretion, but had no effect on the rapid phase. Similarly, taxol, a microtubule-stabilizing drug, selectively reduced the slow phase of LPL release, without influencing the rapid release of LPL into the medium or cellular LPL activity. The rapid heparin-induced release of LPL probably occurs from sites that are at or near the cell surface, and so microtubules must participate in the intracellular transport of LPL from sites of synthesis and glycosylation to the surface binding sites. Heparin-releasable LPL could be resolved into two fractions by chromatography on con A-Sepharose; this pattern of elution was not affected by the prior treatment of cardiac myocytes with taxol.