No abstract

Aust. J. Bioi. Sci., 1977, 30, 289-96 Measurement of plasma progesterone, LH and FSH were made every 6 h during the first 6 days of pregnancy in the mouse. Plasma progesterone and LH were low on day 1, minimum values being recorded at 24 h post coitus. Concentrations of both these hormones started rising during the second half of day 2 with the rise continuing during day 3 to a progesterone peak of 25 ng/ml early on day 4 and an LH peak of 37 ng/mllate on day 4. Levels of progesterone fell during day 4 and LH during day 5 to approximately half their respective peak values and then remained relatively constant over the remainder of the measurement period. Levels of FSH, which were high early on day 1 (180 ng/ml), fell sharply by midday with a small rise late in the day followed by a decline during day 2 to a minimum level of 20 ng/ml at 48 h post coitus. Early on day 3 FSH values rose to 120 ng/ml then fell to 50-60 ng/ml during the next 6 h and remained relatively stable at this level during days 4 and 5. It is suggested that LH is concerned with progesterone production and maintenance of the corpus luteum whilst FSH is concerned with the production of oestrogen required for implantation in this species.

No abstract

A solid-phase tube assay for measuring LH levels in mouse plasma is described. The assay utilizes an antiserum to ovine LH and ovine LH standards and it measures LH levels in 20 III of plasma with a sensitivity of less than 0�6 ng/m!. Various parameters affecting the sensitivity and specificity of the assay were investigated. Serial dilutions of plasma from pregnant mice, a pituitary homogenate from mice and plasma from hypophysectomized mice, injected subcutaneously with ovine LB, ran parallel with ovine LH standards in plasma from hypophysectomized mice and plasma with low LH levels from intact mice. Ovine TSH showed about 12 % cross reaction in the assay system, whilst rat FSH and prolactin and also ovine FSH, prolactin and GH showed practically no cross reaction. Measurements of plasma LH levels have been made in hypophysectomized mice after injection with different vehicles containing 10 or 50llg LH or 50llg FSH per animal. Daily measurements of LH levels throughout pregnancy in the mouse show a rise in LH level prior to implantation and a further rise around mid-pregnancy which drops off sharply to levels which remain fairly constant until parturition when there is another rise.

In hypophysectomized pregnant mice replacement therapy designed to mimic the normal physiological situation showed that FSH in combination with either prolactin or LH, or prolactin plus LH, could initiate implantation in the absence of the pituitary gland. No pituitary hormone was by itself capable of achieving this result. The combination of prolactin with FSH gave better results than a combination of LH with FSH. Prolactin from sheep, cattle or rats was equally effective in combination with ratFSH in initiating implantation. In mice exhibiting suckling-induced delay of implantation this delay was terminated by injection of FSH. GH by itself or in conjunction with other hormones had no significant effect on implantation or on any of the other parameters associated with implantation that were measured.On the basis of these experimental results it is suggested that" prolactin and LH are involved with progesterone production and FSH with oestrogen production, both of which are required for implantation in the mouse.