Follicle-Stimulating Hormone Content of the Pituitary Gland Before Implantation in the Mouse and Rat

Abstract

The method of Lamond & Bindon (1966) was used to measure follicle\x=req-\ stimulating hormone (FSH) in the pituitary glands of mice and rats killed at different times on each of days 1\ p=n-\ 6 of pregnancy. The sensitivity of the method allowed detection of FSH fluctuations not previously described in these species. A significant fall in pituitary FSH occurred in both species on day 3, although it was earlier in the mouse than in the rat. This transient decline in FSH activity, interpreted as a release of the hormone, was followed in both species by a gradual increase on days 4 and 5. Ovarian weight, measured only in the mouse, increased significantly late on day 3 and is believed to reflect changes in pituitary FSH.The results indicate that implantation in the mouse and rat is initiated by altered activity of the pituitary gland during the first 3 days of pregnancy. It appears that this pituitary mechanism differs from that responsible for the events of the oestrous cycle.

Plasma Progesterone, FSH and LH Levels Associated with Implantation in the Mouse

“…Their results showed a rise in LH and prolactin prior to implantation, and FSH values, which were high on day 1, fell sharply on day 2 with no significant increase prior to implantation. This latter result is contrary to the finding of Bindon (1969a) who us€?d a bioassay to demonstrate a significant drop in pituitary FSH content on the morning of day 3 (day 1 is the day of the morning on which the copulatory plug is found). Bindon interpreted this drop in FSH content as a release of the hormone.…”

Bernard Michael Bindon — reproductive physiologist, animal scientist, research leader

“…At that time, there were no suitable assays for sheep or cattle pituitary hormones, and he was instrumental in the development of a successful bioassay for ovine FSH (Bindon 1969b;Martin et al 1969) using the hypophysectomised mouse model which was used for a number of other fundamental studies on male and female reproductive activity in mice (Bindon 1969a(Bindon , 1969b(Bindon , 1969c(Bindon , 1969dBindon and Waites 1968) and sheep (Bindon 1969f, 1971a(Bindon 1969f, , 1971bBindon and Tassell 1969). A colleague, Barrie Restall, who shared a laboratory with Bindon at the time, and collaborated on several projects, recalls the technical skill and speed with which Bindon could hypophysectomise mice, and, given the invasive nature of the technique, his admiration for the very high survival rates and subsequent normal behaviour of these animals.…”