The Conversion of Palmitic Acid into Stearic and Palmitoleic Acids in Rats*

The properties of the depot fats of animals depend, to some extent, upon the nature of the dietary fats. Thus it was shown by Anderson and Mendel (1) that feeding of highly unsaturated oils results in the deposition of a body fat of high iodine number, whereas the administration of “hard” fat in the diet leads to a decrease in the iodine number of the depot fats. Recently Longenecker and Hilditch (2-4) have carefully reinvestigated this problem and they conclude that this change in the composition of the depot fat is due to the direct deposition of individual dietary fatty acids. The effect of variation in diet upon the composition of the depot fat is limited, however, by the fact that all animals have a tendency to reproduce a depot fat with properties characteristic of their species. There are three types of biological reactions which may be responsible for this reproduction of the specific fatty acid mixture: (1) continuous synthesis and simultaneous destruction of fatty acids, (2) selective deposition of such fatty acids as are required and destruction of such dietary fatty acids as are present in excess or are not normal to the depot, (3) interconversion of one fatty acid into another. In regard to the first of these mechanisms, the evidence for the