Glycerolipid biosynthesis in rat adipose tissue. Influence of adipocyte size.

A simple one-step filtration method is described to separate larger adipocytes from the smaller ones by using nylon screen (52 microM pore size). Adipocytes retained on the screen were larger (60-90 micrometers) compared with those that passed through the screen. By using this separation technique, activities of various enzymes involved in triacylglycerol formation from sn-glycerol 3-phosphate were measured in the larger and smaller adipocytes isolated from gonadal fat-depots. The homogenates from larger adipocytes were more active in lipid formation compared with those derived from small adipocytes. This was evident from the increased activities of sn-glycerol 3-phosphate acyltransferase. Mg2+-dependent phosphatidate phosphohydrolase and diacylglycerol acyltransferase in the larger adipocytes. The activities of these enzymes were also measured in the adipocytes isolated from gonadal, perirenal and subcutaneous fat-depots. Subcutaneous adipocytes were smaller and were less active in lipid formation than gonadal and perirenal adipocytes. These measurements in the activities of individual enzymes provide evidence that the entire pathway of esterification via sn-glycerol 3-phosphate is accelerated in the larger adipocytes.