Selective protamine sulphate inactivation of lipoprotein lipase and hepatic lipase in human post-heparin plasma: specific lipase levels in normals and in type I hyperlipoproteinaemia.

The rate of inactivation of triglyceride hydrolase activity by protamine sulphate was determined in pooled, normal, post-heparin plasma. Two distinct first-order rates of inactivation were obtained and the derived constants used to calculate the lipoprotein lipase and hepatic lipase contributions to the total post-heparin triglyceride hydrolase activity in normal controls and in patients with familial hyperchylomicronaemia. The lipoprotein lipase was reduced in the patients whereas the hepatic lipase was normal. There was however a marked age-related increase in the hepatic enzyme activity in normal subjects. Post-heparin lipolytic activity, assayed in vitro against lipoproteins of d less than 1.006 derived from the patients, was markedly reduced in our hyperchylomicronaemic subjects. This assay correlated well with the lipoprotein lipase activity determined by selective protamine sulphate inactivation.