The synthesis of the branched-chain fatty acids of rat skin surface lipid

Abstract

1. 1. The proportions of the iso- and anteiso-branched fatty acids of the rat skin surface lipid were increased by increasing the dietary protein content from 5 to 40% of the total diet. There was a decrease in the proportions of the branched acids when a diet containing 60% protein was fed. 2. 2. Feeding supplements of each of the three branched amino acids, valine, leucine, and isoleucine caused increases in the proportions of the even carbon number iso-, the odd carbon number iso-, and the odd carbon number anteiso-acids, respectively, of the skin surface lipid. For the rats fed isoleucine there was also an increase in the proportion of the odd carbon number normal acids and evidence of the presence of even carbon number anteiso-acids. Both the l- and d-isomers of valine were effective. 3. 3. After injection of l-( 14C 5)valine, there was evidence of the specific labelling of the even carbon number iso-branched acids of the skin surface lipid. The fractions containing the odd carbon number iso- and anteiso-acids were labelled after injection with l-[ 14C 6]isoleucine and dl[4,5- 3H 2]leucine. The odd carbon number normal acids were also labelled in the isoleucine-treated rats. 4. 4. Injection of intact animals with sodium [ i- 14C]-isobutyrate was also followed by labelling of the even carbon number iso-acids, but the recovery of the label in these acids was considerably lower than for the valine-treated rats.