in the Catabolism In Vivo of

To define the roles, In vivo, of hepatic triglyceride lipase and lipoprotein lipase in the catabolism of trlglyceiide-rlch lipoproteins, we Investigated the relationship between the activities of the above enzymes In postheparin plasma and the fractional removal rates of very low density lipoproteins (VLDL) and VLDL remnant particles. In 22 patients, the fractional removal rates of VLDL and VLDL-remnant particles were deter-mined from analyses of the disappearance of radlolodlnated Sf 60-400 and Sf 12-60 lipoprotein B apoproteln. The maximal activities of hepatic triglyceride lipase and lipoprotein lipase were determined in plasma samples drawn 2-60 minutes after heparln injection (60 U/kg). A positive correlation was observed between the fractional removal rate of VLDL and postheparin plasma lipoprotein lipase activity (r = 0.65). When all 22 patients were considered together, no relationship was demonstrable between remnant fractional removal and postheparin plasma lipoprotein lipase activ-ity. However, humans may be subdivided with respect to the way In which they catabollze remnants. In some, all remnant may be catabollzed to form LDL. In others, some of the remnant may also be directly removed from the circulation. Those sub