Lipoprotein lipase distribution in rat adipose tissues: effect on chylomicron uptake.

Adipocytes in the epididymal (Epi) and perirenal (PR) depots of the rat increased continuously in size in rats ranging fromm 50 to 550 g body wt. In contrast, cell size in the subcutaneous (SC) and mesenteric (M) depots was similar to that in the other two depots only until rats achieved 250-350 g. Thereafter, adipocytes in the latter depots were significantly smaller than in the former. In all four depots, the activity of lipoprotein lipase (LPL) per 10(6) cells increased with increasing size in both fed and fasted rats. No significant differences were noted in LPL activity per 10(6) cells between depots as a function of cell size in either nutritional state. During growth, a greater percentage of whole tissue LPL of all depots was sequestered within enlarging adipocytes, resulting in an absolute decrease in activity extracellulalrly. This effect was least pronounced in the Epi and PR depots. In large adipocytes of fed rats, decreased extracellular localization of LPL was paralleled in vivo by decreased uptake of chylomicron triglyceride fatty acids in all depots. In fasted rats, uptake was low and unaffected by changes in cell size in all sites.