GLYCEROL 207 



Stare^^^ found that trilaurm, in which the lauric acid was labeled on the 

 carboxyl group, was well tolerated when given intravenously to rats. 

 Within two hours, 50% of injected C^"* had been excreted as C''*02in the ex- 

 pired air, while a 70% elimination was observed in the 3.5-hour tests. In 

 the case of tripalmitin labeled on C-6 of the acid, Lerner, Chaikoff et alJ'"^ 

 likewise reported utilization, but at a slower rate. After two hours, only 

 7% of the administered C* had been excreted in the expired air, while a 

 total of 50% was accounted for by the respiratory route after twenty-four 

 hours. These experiments, carried out with labeled fatty acids, constitute 

 the best proof of the utilization of fat when given by the mtravenous route. 

 Creditor^^^ observed that intravenous fat emulsions produced an in- 

 creased mechanical fragility of the red blood cells of dog and human blood. 

 Sometimes a spontaneous intravascular hemolysis has been noted in humans 

 who have received these emulsions. It is suggested that the "highly emulsi- 

 fied fat might well distribute itself around the red cell and alter the mem- 

 brane relationships m such a way that fragiUty is increased." Waddell and 

 co-workers'^" reported that the removal of emulsified fat from the blood is 

 a first-order reaction, irrespective of the chemical composition of the oil, 

 except where gelatin is used as an emulsifying agent. Cannon et alJ^^ 

 reported that, when rats were injected subcutaneously with protein hy- 

 drolysates, intraperitoneal or intravenous fat augmented amino acid 

 utilization. 



3. The Oxidation and Metabolism of Glycerol 



Just as glucose can be considered to be a mother substance in the syn- 

 thesis of glycerol, so the oxidation and metabolism of glycerol are bound up 

 with that of glucose. Doerschuk^^^ reported that, when glycerol- l-C* was 

 administered to a normal intact rat, the main route of metabolism consisted 

 of phosphorylation and oxidation ; over 80% of the total glycerol followed 

 this pathway. The intermediary products, in all probability, involve those 

 suggested in the synthesis of the trihydric alcohol from glucose, and the 

 order of formation is the reverse of the synthetic reaction. 



'" R. P. Geyer, J. Chipman, and F. J. Stare, /. Biol. Chem., 176, 1469-1470 (1948). 



'55 S. R. Lerner, I. L. Chaikoff, C. Entenman, and W. G. Dauben, Science, 109, 13 

 (1949). 



"6 M. C. Creditor, Proc. Soc. Exptl. Biol. Med., 82, 83-87 (1953). 



'"W. R. Waddell, R. P. Geyer, I. M. Saslaw, and F. J. Stare, Atn. J. Physiol. 174, 

 39-42 (1953). 



'58 p. R. Cannon, L. E. Frazier, and R. H. Hughes, Federation Proc, 12, 385 (1953). 



^" A. p. Doerschuk, J. Biol. Chem., 193, 39-44 (1951). 



