Pregnancy in Cholesterol Fed Rats

Abstract

The disturbances in blood cholesterol level known to be associated with pregnancy, and the prevailing impression that pregnancy may increase the incidence of diseases associated with abnormal cholesterol deposition have indicated the desirability for study of the influence of cholesterol feeding during pregnancy.

There is strikingly little record of such a study in the literature. Schönheimer 1 reported that pregnant animals were more subject to the deposition of anisotropic fat than non-pregnant ones. He reports feeding cholesterol to a rabbit which became very sick 14 days after mating and showed resorption of 3 fetuses with one fetus dead at term and abnormal deposition of anisotropic fat in the placenta.

We have used rats for the present study. These were placed at weaning on a diet made up of 20 parts raw casein, 4 parts Osborne and Mendel salts, 4 parts agar, 15 parts Crisco, and 57 parts starch, with one part cholesterol dissolved in Crisco and incorporated in the diet. Vitamin supplements were given separately 3 times a week as yeast, tiki-tiki, or yeast extract for B, and tuna or sea bass liver oil standardized in this laboratory and diluted with corn oil for A and D. With tiki-tiki, raw casein supplied G. After successful mating was demonstrated by the finding of sperm, the protein in the diet was increased to 26% and the starch decreased to 51% and the vitamin B increased 2 to 4 times (in different groups). This diet was modeled on that shown by Morgan and Simson 2 in this laboratory to be adequate to meet the food requirements of the rat during pregnancy.

Vaginal smears were taken daily after the rats were approximately 90 days of age. In general cycles tended to be lengthened by one to 2 days. They were not altered, nor was the mating performance of the animals changed when, at the suggestion of Mrs. O. H. Emerson, a wheat germ oil preparation of tested potency in amounts several times that necessary to supply the vitamin E requirement for normal pregnancy in the rat was given to half the animals. Some difficulty was experienced in obtaining successful matings with cholesterol-fed animals. There seemed, however, to be no difference, either in fertility or in difficulty of mating when cholesterol-fed males or males on stock diets were used. Likewise, cholesterol-fed males showed no loss of fertility when mated with stock females.