Selective Measurement of Two Lipase Activities in Postheparin Plasma from Normal Subjects and Patients with Hyperlipoproteinemia

Abstract

A B S T R A C T An assay has been developed for specific measurement of two different lipase activities in postheparin plasma. Lipoprotein lipase, derived from extrahepatic sources, is measured as protamine-inactivated lipase activity; hepatic lipase activity is protamine-resistant under the conditions of this assay. In 100 normal subjects, both enzyme activities were noted to be related to age and sex. Protamine-resistant lipase, which comprised 46-95% of the total activity, was highest in men over 18. Protamine-inactivated lipase activity was greatest in younger males and was agecorrelated in women, doubling between the second and sixth decades.In 12 patients with hyperchylomicronemia, including five previously shown to have familial type I hyperlipoproteinemia, protamine-inactivated lipase activity was markedly reduced, whereas protamine-resistant lipase was below normal in only 1. The results were not due to lack of plasma activator, presence of plasma inhibitor, or diet, and the deficiency was not overcome by increasing the provoking dose of heparin from 10 U to 75 U/kg. Mean values for both lipase activities were not reduced in 32 other patients with hyperchylomicronemia, nine with "floating beta" lipoproteins (type III hyperlipoproteinemia), and 23 with hyperprebetalipoproteinemia (type IV). Mean protamine-resistant lipase activity was below normal in a group of four women with hypothyroidism, in whom protamine-inactivated lipase was not reduced. Both of the lipase activities were capable of hydrolyzing lipid in very low-density lipoproteins, but the relative rate of hydrolysis of chylomicrons by protamine-resistant lipase was markedly limited. These results indicate the importance of distinguishing between lipases of hepatic and extra-

In vitro activation of the enzymic activity of hepatic lipase by apoA‐II

“…The regulation of HL activity has received much less attention [3,14] and there has been, to our knowledge, no previous report of specific activators of this enzyme. It is known, however, that HL enzymic activity is enhanced by the addition of serum [ 14].…”

“…Human post-heparin plasma contains two major lipase activities designated lipoprotein lipase (LPL) and hepatic lipase (HL) [1][2][3]. LPL is activated by apoC-II [4,5] and aport (/32 glycoprotein I) [6].…”

Effect of exogenous hyperinsulinaemia on atherogenesis in cholesterol-fed rabbits

“…At weeks 20 and 22, postheparin plasma lipoprotein lipase and hepatic lipase activities were measured as follows [9,10]: between 3 and 4 h after the daily meal, blood samples were drawn into disodium EDTA, 10 min after intravenous injections of 200 units of heparin per kg body weight (SAD, Copenhagen, Denmark). Blood and plasma were kept at 4°C before freezing at -80°C until assayed in duplicate Atherosclerosis.…”

Metabolic Disorders of Serum Lipoproteins in Endotoxin‐Poisoned Mice: The Role of High Density Lipoprotein (HDL) and Triglyceride‐Rich Lipoproteins

“…There was no appreciable difference in total serum cholesterol between the control and the poisoned mice. On the other hand, the HDL-cholesterol level in the poisoned mice decreased slightly 3 hr post intoxication, fell to a much lower level than that in the control mice at [18][19][20][21][22][23][24] hr, and then tended to increase to the normal range. However, the LDL-cholesterol content of endotoxin-poisoned mice increased about 175% compared with that of the control mice at 18-24 hr, and returned to the normal level at 48 hr.…”

“…Recently, post-heparin lipolytic activity (PHLA) was reported (22,23) to con-sist of both extrahepatic triglyceride lipase (LPL) and hepatic triglyceride lipase (H-TGL) activities. LPL and H-TGL are clearly different in their physiological roles.…”