Diurnal changes in the fatty acid patterns of rat liver lipids
Wadhwa, P.S.; Elson, C.E.; Pringle, D.J.
Journal of Nutrition 103(6): 899-903
1973
ISSN/ISBN: 0022-3166 PMID: 4705275 Document Number: 61914
Male Holtzman rats of bodyweights 100 to 200 g were kept in a temperature controlled room lit from 0600 to 1800 h daily and were fed on a semisynthetic diet of casein hydrolysate 16.5, lactalbumin hydrolysate 2.0, methionine 0.3, maize starch 17.0, sucrose 17.0, dextrin 16.0, cellulose 4.8, salt 4.0, vitamin mixture 6.5 and maize oil, with oleic and linoleic acids as the main fatty acids, 16.0%. The rats were allowed food freely or to eat hourly 1/24 of the total food eaten by those fed to appetite. After 3 to 4 weeks the rats were killed at 0600, 1200, 1800 or 2400 h and the lipid fractions of the liver were estimated by thin-layer chromatography and their fatty acid composition by gas-liquid chromatography. With feeding to appetite the composition of liver triglycerides was slightly affected by diurnal cycles associated with each fatty acid. Linoleate and, to a less extent, oleate increased sharply from 1800 to 2400 h and decreased to a minimum at 1800 h. For stearate the cycle was reversed. Arachidonate declined from 2400 to 1200 h and rose sharply from 1200 to 1800 h, falling during the next 6 h. There were significantly higher proportions of arachidonate and stearate in triglycerides of the livers of rats fed hourly. The contribution of linoleate, oleate and palmitate to liver phospholipid profile was constant throughout the day in the rats feeding freely. In the other group the cycle of phospholipid fatty acids appeared to be 12 h out of phase with that of rats fed to appetite. Changes in the fatty acid profile of cholesterol esters of rats fed hourly, but not of the other group, resembled those of triglycerides.