1. Fat-free homogenates from the epididymal fat-pads of rats were used to measure the rate of palmitate esterification with different substrates. The effectiveness of the acyl acceptors decreased in the order glycerol phosphate, dihydroxyacetone phosphate, 2-octadecenyl-glycerol and 2-hexadecylglycerol. 2. Glycerol phosphate and dihydroxyacetone phosphate inhibited their rates of esterification in a mutually competitive manner. 3. The esterification of glycerol phosphate was also inhibited in a partially competitive manner by 2-octadecenylglycerol and to a lesser extent by 2-hexadecylglycerol. However, glycerol phosphate did not inhibit the esterification of 2-octadecenylglycerol. 4. The esterification of dihydroxyacetone phosphate and 2-hexadecylglycerol was more sensitive to inhibition by clofenapate than was that of glycerol phosphate. Norfenfluramine was more effective in inhibiting the esterification of 2-hexadecylglycerol than that of glycerol phosphate or dihydroxyacetone phosphate. 5 It is concluded that rat adipose tissue can synthesize glycerolipids by three independent routes.
