Effect of chronic consumption of a high-fat diet on mammary metabolism.

Rats have been fed semi-synthetic diets containing 4 and 20% (w/w) corn oil for periods of 9-12 weeks covering two lactations. The mean maternal and pup weights at day-14 of the second lactation on the diets were not significantly different. The milk fatty acids of the rats on the high-fat diet contained 39 mol% linoleic acid and only 20 mol% medium-chain acids compared with over 40% for the low-fat diet. With the exception of "malic" enzyme, none of five enzymes assayed in mammary supernatants was significantly altered by the diet fed. These results suggest that the synthesis of these enzymes in the mammary gland is insensitive to dietary lipid.