Variations in Some Biochemical and Histological Characteristics of Bovine Corpora Lutea during Early Pregnancy

Abstract

Two experiments involving 40 heifers were used to study the level of function of the corpus luteum during early pregnancy. Experiment one was a comparison of day-14 of the estrual cycle and day-14, -28, and -42 of pregnancy. Experiment two compared day-18, -23, and -28 of pregnancy. Progesterone and total progestogen were lower (P<0.01) on day-28 and -42 of pregnancy than on day-14. A significant (P<0.01) negative regression of progesterone and total progestogen content on day of pregnancy up to day-28 was found ( — 6.07 and —6.32 mcg., respectively). These regressions appeared to be linear. The level of 4-pregnene-20β-o1-3- one did not appear to vary with stage of pregnancy. Free cholesterol concentration increased significantly between day-14 and -28, but tended to return toward the day-14 level by day-42. The regression of free cholesterol between day-14 and -28 of pregnancy was 35.6 mcg. per gram per day (P<0.01) and appeared to be linear. Mean concentrations of DNA were not different, but RNA decreased with increasing length of gestation. A decreased percentage of functional cells was apparent histologically at day-23 of pregnancy and at later stages as compared to day-14 or -18 of pregnancy. The latter named stages in turn had fewer functional cells than the unbred heifers on day-14 of the estrual cycle. Copyright © . .