3H-Estradiol Uptake and Retention by Target Tissues of Light-Sterilized Female Rats

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Abstract
Tissue distribution of radioactivity was studied at 2, 4 and 6 h after i.v. injection of 3H-estradiol-17.beta. (41.7 ng/100 g body wt) in 12 light-sterilized and 11 control female rats ovariectomized 72 h prior to injection. Female rats were light-sterilized by exposure to continuous illumination for 82 days and, based on the duration of continuous vaginal cornification and the absence of corpora lutea at post-mortem histological examination of the ovaries, were anovulatory for at least 30 days prior to injection. Control rats were housed under conditions similar to the experimentals but were exposed to alternating lighting (14 h light:10 h dark). They remained ovulatory throughout the experiment. Uterine 3H-estradiol uptake and retention were significantly depressed in the light-sterilized group. There were no significant differences in 3H-estradiol uptake or retention as a result of light-sterilization in any of the other tissues studied, including anterior, middle and posterior hypothalamus, hippocampus, amygdala, cerebrum, anterior pituitary and plasma. The failure to detect a reduction in neural 3H-estradiol uptake demonstrated that the anovulatory state could exist without a concomitant reduction in the hypothalamic estrogen binding capacity. The possibility was discussed that the decreased target tissue binding noted in various types of anovulatory animals was the result, not the cause, of altered ovarian function.