Pulse-chase study on lipoprotein lipase in perfused guinea pig heart.

Lipoprotein lipase (LPL) in guinea pig hearts was labeled by perfusion for 15 min with [35S] methionine, followed by chase perfusion with unlabeled medium for less than or equal to 90 min. Suitable conditions for pulse and chase and for immunoprecipitation of LPL were worked out. Differences in labeling between individual hearts were found to be substantial. A technique to take serial biopsies (approximately 20 mg) from the heart ventricle was therefore worked out and validated. Regional differences of LPL labeling within the ventricle were small. There was no evidence for enhanced release of LPL caused by biopsy. When heparin was present throughout the chase, labeled LPL began to appear in the medium after 30 min. Thus LPL can move rapidly from synthesis in parenchymal cells to the endothelial surface and into the medium. After 90 min chase with heparin, approximately equal amounts of LPL (approximately 32%) had been released to the medium, remained in the heart, or had been degraded, respectively. In contrast, no detectable amount of labeled LPL appeared in the medium during 90 min chase without heparin, and a heparin flush at this time brought out only approximately 9% of the pulse-labeled LPL.