The liver-lipid constituents of male and female rats. 2. Effects of the fat-deficiency syndrome, aggravated by dietary cholesterol

Feeding cholesterol to rats depresses liver vitamin A concentrations in male rats but not in females (Green, Homer, Lowe & Morton, 1957).The difference between the sexes in this effect of cholesterol suggested that there might be a metabolic link with the essential fatty acids.It has been shown, however, that deficiency of these essential fatty acids did not itself affect liver vitamin A levels in either sex (Morton & Homer, 1961).The experiments reported below were begun at the same time as those just referred to and differed only in that all the animals had 1 % of cholesterol added to their basal fat-free diets.Previous work (Peifer & Holnan, 1955; Holman & Peifer, 1960) had shown that dietary cholesterol accelerated the onset of fat deficiency.Our first aim was to find how the cholesterol- supplemented diets influenced liver vitamin A levels.During this investigation interrelationships between essential fatty acids and either endogenous cholesterol (Morton & Homer, 1961) or exogenous cholesterol were examined.EXPERIMENTAL Animals and diets.Hooded rats were fed on a basal fatfree diet fromweaning.This differed from the diet described by Morton & Homer (1961) in that 1% of crystalline cholesterol (Croda Ltd.) was included at the expense of an equal weight of sucrose.Procedure.The experimental plan resembled that described for rats that did not receive cholesterol (Morton & Homer, 1961).Ten males and twelve females from six litters delivered within a period of six days were given the basal diet at weaning.The experimental groups were formed when weaning was completed.In group 2 five males received the basal diet.In group 1 five males received the basal diet plus 100 mg. of linoleic acid per day.In group 4 six females received the basal diet.In group 3 six females received the basal diet plus 25 mg. of linoleic acid per day.The diets were fed ad lib.and water was freely provided.Linoleic acid was given as cottonseed oil.The males were killed after 78-81 days.The females were killed between the 138th and 146th days.