Species, diet, and gender differences in plasma postheparin lipolytic activities in nonhuman primates. Relationships with plasma lipids and high density lipoproteins.

Abstract

Studies were done in selected groups of nonhuman primates in which the diet (low fat and high fat as either polyunsaturated or saturated fat), gender, and species (African green monkeys and cynomolgus monkeys) were varied. Large differences in plasma lipid and lipoprotein concentrations were found among these groups, providing the opportunity to examine their relationships to postheparin lipolytic activities (PHLA) including lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL). PHLA was measured in plasma drawn 20 minutes after injection of heparin (100 units/kg). The assay was done with a radioactive triglyceride emulsion, and LPL and HTGL activities were estimated after 1 M NaCl inhibition of the former. LPL activity was high in both species of monkeys, and HTGL activity was low; the ratio of HTGL/LPL was consistently less than 0.5. The mean values for LPL activity did not vary significantly among experimental groups, but significant negative correlations between LPL activity and plasma triglyceride concentration were found. Statistically significant diet, species, and gender differences in HTGL activities were found. In high-fat-fed compared to low-fat-fed animals, HTGL activities were higher, and high density lipoprotein (HDL) cholesterol concentrations and the percentages of HDL2b were also higher. African green monkeys had consistently higher HTGL activities than cynomolgus monkeys and had higher concentrations of HDL cholesterol and a greater proportion of HDL as the larger HDL2b subfraction. Significantly lower HTGL activities were found in females compared to males fed the low-fat diets, and females had a significantly greater proportion of total HDL in the HDL2b subfraction.(ABSTRACT TRUNCATED AT 250 WORDS)