Progesterone receptors in the endometrium of normal and repeat-breeder cows

Progesterone receptors were measured in the cytosol and nuclear fractions of endometrial cells from repeat-breeder (RB) and normal (NB) cows on day 6 post-breeding (inseminated group) and on days 3, 6 and 7 after estrus (non-inseminated group). Results were related to both the type of cow and the condition of the embryo present within the uterus in the inseminated groups. Cows carrying morphologically abnormal embryos showed higher concentrations of cytosolic progesterone receptors as compared with the normal group, regardless of the type of cow. Within the normal embryo group, RB cows had higher concentrations of progesterone receptors than NB. The same tendency toward higher concentrations of progesterone receptors in RB cows was observed in the non-inseminated groups. The results of this study suggest the existence of a local hormonal imbalance, which may be related to the repeat-breeding problem.