By means of the modified HCG augumentation method of Steelman-Pohley for FSH and the modified ovarian ascorbic acid depletion method of Parlow for LH, FSH and LH content of the pooled anterior pituitaries from the same groups were simultaneously determined. The results were as follows:
1. In mature female rats, a significant, progressive increase was found in both FSH and LH content after gonadectomy, accompanied by the appearance of castration cells.
2. Most of the post-partum ovulations in this study were found to occur between the night of Day-1 and the morning of Day-2, by examination of vaginal smears and histological findings of the ovaries.(Day-0-arturition).
A dramatic fall in LH content from a higher. level in late pregnancy to a significantly lower value on Day-1 may be interpreted as providing the LH release into the circulation responsible for postpartum ovulation.
On the other hand, FSH content did not show a significant decline until Day-2. The significance of the time lapse between the change in LH and FSH content appears very interesting but requires further studies for an appropriate explanation.
3. FSH and LH content of the pituitary during lactation after post-partum Day-3 did no have significantly different concentrations from those in cyclic rats.
The marked decrease in ovarian weight and the histological findings of ovarian suppression indicate lower FSH and LH levels in the circulation.
These results suggest that the production and release of FSH and LH are inhibited during lactation, probably by the suckling process.
View full abstract