Atherosclerosis, 41 (1983) 241-250 Elsevier Scientific Publishers Ireland, Ltd. 241 Pre- and Post-Weaning Milk Consumption Effects on Lipid Metabolism in Rats David Kritchevsky, Shirley A. Tepper, Maryann A. Mueller *, Susanne K. Czarnecki ** and David M. Klurfeld The Wwtar Institute of Anatomy and Biology, 36th Street at Spruce, Philadelphia, PA 19104 (U.S.A.) (Received 7 October, 1982) (Accepted 6 January, 1983) zyxwvutsrqponmlkjihgfedcbaZYXWVUTS Summary Pregnant Sprague-Dawley rats were given milk or water as their drinking fluid during the last third of their pregnancy and after birth of their pups. At 30 days of age offspring were placed on either milk or water yielding four groups: suckled to milk drinking dam, weaned to water or milk (milk-water and milk-milk) or weaned to water drinking dam, placed on water or milk (water-water, water-milk). After 5 weeks, rats were killed and serum and liver lipids, cholesterol absorption and activity of hepatic enzymes of lipid metabolism were determined. Rats drinking milk obtained more calories from fluid and less from solid food. Pups suckled to water drinking dams weighed significantly less at weaning but gained more weight during the post-weaning period. The milk-water group ingested fewer calories than the other three. There were no significant differences in serum or liver lipids among the four groups. Cholesterol absorption was higher in the two groups suckled to milk-drinking dams, who excreted about 40% less fecal neutral steroid and 30% less acidic steroid. Hepatic HMG-CoA reductase activity was similar in all groups but cholesterol 7a-hydroxylase activity was 180% higher in rats suckled to water-drinking dams. Hepatic fatty acid synthesis activity was elevated in rats given water in the post-weaning period regardless of the dam’s drinking regimen. The data suggest that milk affects aspects of lipid metabolism in young rats in a complex fashion. The Supported, in part, by Grants HL-03299 and CA-09171 and a Research Career Award (HL-00734) from the National Institutes of Health and by grants-in-aid from the National Live Stock and Meat Board, the W.W. Smith Charitable Trust and the Commonwealth of Pennsylvania. * Present address: Department of Food Science and Human Nutrition, Michigan State University, East Lansing, MI 48824, U.S.A. ** Present address: National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20205, U.S.A. 0021-9150/83/$03.00 0 1983 Elsevier Scientific Publishers Ireland, Ltd.