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ABSTRACT

The patterns of peripheral progesterone concentrations were investigated in a number of murine models on a 13 h light: 11 h darkness lighting regime. The pattern in the intact mouse at dioestrus was compared with that in the ovariectomized mouse. A diurnal pattern was recorded in both, maxima occurring around the end of the light period; no conspicuous nadir was recorded, levels of progesterone remaining relatively constant over a 14-h period. Adrenalectomized mice displayed no such rhythm, indicating that the adrenal is responsible for any diurnal rhythm in peripheral plasma progesterone concentrations at dioestrus. At pro-oestrus in intact animals a similar rhythm was observed, but the maximum levels of progesterone were approximately five times greater than at dioestrus and, moreover, persisted in adrenalectomized mice, indicating that the rhythm of adrenal secretion of progesterone is masked by ovarian secretion. Ovariectomized mice with implants of oestradiol-17β displayed a similar rhythm to that of intact mice at dioestrus, but had significantly higher plasma progesterone levels around the time of the maxima although not over the total 24-h period. An s.c. injection of oestradiol benzoate superimposed on oestrogen levels produced by implants had no significant effect on plasma progesterone levels. Also at pro-oestrus the pattern of peripheral LH concentration was investigated in both the intact and the adrenalectomized mouse. For both, maxima were recorded just before darkness, at 19.00 h, in advance of the progesterone surge. In adrenalectomized mice this surge at 19.00 h was attenuated. The possible role of adrenal progesterone in ovulation and the mechanisms by which endogenous oestrogens might enhance adrenal progesterone output are considered.

J. Endocr. (1987) 112, 15–21

SUMMARY

Gonadotrophins were injected into mated hypophysectomized and suckling mice in an attempt to induce implantation. In these two classes of animal implantation is normally delayed by absence or suppression of pituitary gonadotrophin release. Antibodies raised against ovine gonadotrophins were injected into mice soon after mating in an attempt to inhibit implantation.

Pregnant mare serum gonadotrophin (PMSG) was effective in inducing implantation in both hypophysectomized and in suckling mice. This may mean that a gonadotrophin with the qualities of PMSG normally initiates implantation. Alternatively, PMSG may have been effective by virtue of its long half-life rather than any special hormonal attributes. Human chorionic gonadotrophin was ineffective in both types of mouse. Mixtures of ovine follicle-stimulating hormone (FSH) and luteinizing hormone (LH) (100 μg of each), injected daily for 3 days, were necessary to induce implantation in hypophysectomized mice.

Implantation was readily induced in suckling mice by a single injection of FSH (equivalent to 12·5 μg NIH-FSH-S3) prepared from rat pituitary glands.

Implantation was readily inhibited by anti-ovine LH. Anti-ovine FSH was ineffective but this did not cross-react with mouse FSH.

SUMMARY

When the uteri of lactating mice were traumatized from 4 to 16 days post partum, deciduomata were formed in only one of thirty-one animals. However, when progesterone in doses of 0·25 mg or more was administered for 3 days after traumatization, sixteen out of eighteen lactating mice formed deciduomata. It was established that at least 0·35 mg progesterone daily for 7 days is required to induce the decidual reaction in ovariectomized mice.

Although there is ample evidence for the secretion of progesterone during lactation in the mouse, the amounts are apparently insufficient to initiate and maintain deciduomata. It is concluded that quantitative differences exist between the pseudopregnancy of lactation and of sterile coitus.

The most important recent investigations of the cytology of the parathyroid gland in mammals are those of Rosof [1934] and de Robertis [1940,1941], both of whom studied the rat. These investigators described the Golgi apparatus and mitochondria, the former correlating changes in them with the phases of a secretory cycle and the latter describing a reduction of the Golgi material after injection with parathyroid extract and a hypertrophy after the experimental induction of rickets on a low-calcium and low-phosphorus diet. Both workers observed dark osmiophil and light non-osmiophil cells, and de Robertis described a disappearance of the dark cells following parathyroid-extract injection and an increase with low-calcium and low-phosphorus diets.

With a view to carrying out similar experimental studies on the mouse parathyroid the present investigation of the normal cytology was first undertaken. It was also of interest to discover whether the rather complicated secretory cycle described by Rosof was