Hypophyseal LH and FSH release and uterine nucleic acid changes during the mouse estrous cycle

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Abstract
Concentrations of hypophyseal and plasma luteinizing hormone (LH) and follicle stimulating hormone (FSH) were measured along with the total amount of uterine DNA and RNA during four stages of the mouse estrous cycle: proestrus, estrus, metestrus, and diestrus. Female mice were exposed to male olfactory stimuli to induce repeatable 4–5 day estrous cycles. The mean concentration of hypophyseal LH dropped from 2.9 μg/mg at diestrus to 0.3 μg/mg at proestrus. During this same time period the concentration of plasma LH increased from 3.3 μg/100 ml to 10.6 μg/100 ml. In contrast to the fluctuations in LH, the concentration of FSH in the hypophyses and plasma remained relatively constant throughout the estrous cycle. Uterine weight and total uterine DNA, RNA, and the ratio of RNA:DNA were all significantly greater (P < 0.05) at proestrus than at metestrus suggesting significant fluctuations in cell numbers and protein synthetic activity of the uterus during the estrous cycle. The fluctuations in LH and FSH release and in uterine nucleic acids noted during the mouse estrous cycle generally agree with observations in laboratory rats. However, the pattern of LH and perhaps FSH release preceding ovulation in mice may be different than that suggested for rats. These differences may be attributed to the greater dependence of mice on male olfactory stimuli.