Effect of marginal zinc deficiency on lipoprotein lipase activities in postheparin plasma, skeletal muscle and adipose tissues in the rat.

The activities of lipoprotein lipase in postheparin plasma, retroperitoneal adipose and gastrocnemius muscle tissues were determined in the rats fed 2.8 ppm of dietary zinc for eight weeks, as compared with pair-fed and ad libitum-fed rats given 30.8 ppm of zinc. The postheparin lipoprotein lipase activity, as determined by using a lipid emulsion labeled with [3H]triolein as the substrate, was significantly lower in the first group of rats, relative to that in the second and third groups. Tissue lipoprotein lipase activities were compared using the lipid emulsion and activator serum obtained from the zinc-deficient rats and the ad libitum-fed rats. The activator sera were devoid of very low density and low density lipoproteins, but enriched in high density lipoproteins. Muscle lipoprotein lipase activities were significantly lower when assayed with the activator serum from the zinc-deficient compared with the activities determined with the activator serum from the ad libitum-fed. Similarly, muscle lipoprotein lipase activities were lower in all groups when [3H]-triolein-labeled chylomicrons from the zinc-deficient were used as the substrate, compared with the activities determined using the chylomicrons from the ad libitum-fed. Lipoprotein lipase activities in the adipose tissues were not affected by the different sources of the activator sera and chylomicrons. The results strongly suggest that the decrease in postheparin lipoprotein lipase activity in zinc deficiency is not due to changes in tissue lipoprotein lipase enzyme per se, but to compositional alterations in chylomicrons and high density lipoprotein, particularly, with regard to C apolipoproteins, modulators of lipoprotein lipase activity.