290 



ESSENTIAL FATTY ACIDS 



use to samples in which Unoleic acid is the major component. Empirical 

 conditions might be found to extend its usefulness as a micromethod. 

 Because of its specificity, the enzymatic method should be useful in meas- 

 urement of total essential fatty acids on a microscale. 



D. ANIMAL ASSAY 



Recently a method has been developed for the assay of essential fatty 

 acids by measurement of the growth response induced by supplementing 

 fat-deficient rats with the test fat.^^ Male rats maintained on a fat-deficient 

 diet until growth ceased resumed growth when they were given supplements 

 containing linoleate, and this growth has been shown to be proportional 



LOG DOSE- MILLIGRAMS 



Fig. 6. Relationship between weight gain and logarithm of dose of linoleate in 

 male fat-deficient rats.'^ 



to the logarithm of the linoleate dose. This proportionality is shown in Fig. 

 6. This assay has been used to measure the essential fatty acid content 

 of butter and margarine.'^ 



The advantage of this assay is that it measures physiological response, 

 non-active isomeric forms which would be measured by other analyses not 

 affecting the assay. It suffers the disadvantages of the inaccuracy of bio- 

 logical assay methods, the large sample required, and the long time con- 

 sumed for the assay. 



15 S. M. Greenberg, C. E. Calbert, E. E. Savage, and H. J. Deuel, Jr., J. Nutrition 

 41,473 (1950). 



16 H. J. Deuel, Jr., S. M. Greenberg, L. Anisfeld, and D. Melnick, J. Nutrition 45, 

 535 (1951). 



