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1. The in vitro basal lipid metabolism of rat pancreatic fragments was compared with that in adipose tissue fragments and liver slices. 2. [1-14C]Acetate added to the media was mostly incorporated into palmitic acid and to a lesser extent into oleic acid. In addition, pancreatic tissue exhibited a marked capacity for elongation of polyunsaturated fatty acids by [1-14C]acetate and resulting desaturation when compared to adipose tissue and liver. 3. Data obtained in the presence of [U-14C]glucose, [1-14C]palmitate and 3H20 indicate that acetyl-CoA derived from glucose and from beta-oxidation of fatty acids contributed to de novo lipogenesis. 4. Oxidation of [1-14C]palmitic acid was 9-13 times higher in the pancreas than in adipose tissue or liver when expressed on a wet weight basis. 5. The fatty acid moiety of pancreatic glycerolipids could be derived from de novo synthesis, fatty acids added to the medium, or from fatty acids formed from the hydrolysis of endogenous lipids. The glycerol moiety could be derived either from glucose, or directly from glycerol through participation of glycerol kinase.

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1.The 700 x g fat-poor internatant from epididymal adipose tissue homogenate of fasted refed rats was incubated a t pH6.5 with 0.5mM [1-l4C]acetate in the presence of cofactors. After incubation, six lipid classes were separated by thin-layer chromatography and their fatty acids analyzed by radio gas-liquid chromatography. The incorporation of [ 1 -14C]acetate into glycerides was limited by the activity of acetyl-CoA carboxylase, and was stimulated two to three-fold by the addition of 0.1 mM unlabelled malonyl-CoA.2. The chain-length of fatty acids labelled in vitro was controlled by the relative concentrations of malonyl-CoA and acetyl-CoA. Addition of unlabelled malonyl-CoA influenced the operation of fatty acid synthetase in such a way that the ratio of radioactive palmitate to radioactive myristate increased markedly.3. sn-Glycerol 3-phosphate stimulated the esterification of fatty acids into triglycerides. Under these conditions whereas the specific activity of free fatty acids was much higher than that observed in triglycerides, the specific activity of diglycerides was low, when compared to the same triglycerides. Newly synthesized monounsaturated fatty acids were preferentially esterified into triglycerides. 0.5 mM [1-14C]palmitate was efficiently incorporated into triglycerides but not into diglycerides.Given any cell size and cellular proliferation rate, the intermediary metabolism of adipocytes is regulated by the concentration and activity of proteins, the levels of metabolites and by hormones. After having explored lipid metabolism in epididymal adipose tissue fragments and isolated fat cells [1,2], an investigation was made of de novo fatty acid and glyceride synthesis in 700 x g adipose tissue internatants. This system includes "natura1" proportions of both soluble proteins and the proteins of several adipose cell organelles (mitochondria, microsomes and liposomes). The conditions were aimed at testing the activity of acetyl-CoA synthetase, acyl-CoA synthetase, -dehydrogenase and -elongase, and the esterifying enzymes of Kennedy's pathway. In some instances, acetyl-CoA carboxylase was also investigated.Detailed studies of the activity of fatty acid synthetase have been reported in liver [3], mammary Enzymes.

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