Diurnal variation in uterine estrogen receptors in immature female rats--inhibition by arginine vasotocin.

A diurnal variation in uterine estrogen receptors from immature female rats was observed with the peak occurring during the mid-light phase (noon) of the cycle. Although no dose response was noted, all concentrations of arginine vasotocin ranging from 5 x 10(-7) to 5 x 10(-9) significantly inhibited binding of 3H-estradiol to estrogen receptors in the cytosol fraction of uteri obtained from immature female rats either during the light or dark phase of the photoperiod.