Selective release of extrahepatic lipoprotein lipase by polymetaphosphate

We have studied the lipase released into the circulation by polymetaphosphate injection into rats. Lipase release was in proportion to the dose injected. The post-polymetaphosphate lipase was almost completely inhibited by high salt concentrations or by addition of protamine sulfate to the assay system suggesting that this compound released lipoprotein lipase and not hepatic triglyceride lipase. The lipases released by polymetaphosphate and by heparin were compared using a heparin-sepharose affinity column technique which separates lipoprotein lipase from hepatic triglyceride lipase. While heparin released both lipoprotein lipase and hepatic triglyceride lipase, polymetaphosphate released almost exclusively lipoprotein lipase. Other experiments showed that neither polymetaphosphate nor heparin inhibited the hepatic lipase when added to the assay. These results suggest that lipoprotein lipase may be released by the negative charge on these high-charge polymers while hepatic triglyceride lipase release may require the specific sugar configuration of heparin.