The Effects of Progesterone, Testosterone and Ergocornine on Non-Pregnant and Pregnant Guinea-Pigs

Abstract

In guinea-pigs absorbing 0\m=.\1 mg or more progesterone daily from solid, subcutaneous tablets, follicles grow and regress normally as do existing corpora lutea, but ovulation is completely inhibited. The uterus, in the absence of cyclic changes, is continuously stimulated by ovarian oestrogens in progesterone-treated animals. It enlarges, sometimes becoming enormous, and shows various pathological changes.These are absent from the uteri of ovariectomized animals treated with progesterone. Five males which absorbed 0\m=.\26to 1\m=.\7 mg progesterone daily for 30 to 64 days had normal reproductive organs.Testosterone propionate, similarly administered, also inhibits ovulation; additionally it leads to a reduction in follicle growth and ovary size. Both steroids showed steady, slow rates of absorption as determined from tablet weights before and after implantation.Ergocornine, which is said to inhibit corpus luteum secretion in rats, had no such effect on corpora lutea in non-pregnant and pregnant guinea-pigs, when injected in solution. 272Ruth Deanesly Bouin's fluid and sectioned serially at 7 µ. Uteri were weighed after fixation and transfer to 70% alcohol. The ergocornine methane sulphate was dissolved in 20% alcohol and injected subcutaneously. Absorption from the progesterone tablets, weights up to 50 mg, proceeded slowly at a steady, fairly uniform rate (Tables 1, 2 and unpublished data) ; tablets remained solid and could be cleaned and re-used with similar results.Rates of absorption varied with the initial size and number of the tablets implanted. Plasma progesterone levels remained low in all progesterone treated, non-pregnant, normal or ovariectomized animals whose blood was examined. These levels, 2 to 3 ng/ml, were generally in the lower range of those recorded for non-pregnant guinea-pigs (1 to 13 ng/ml) by Heap, Perry & Rowlands (1967), but in ovariectomized animals with large amounts of progesterone (Table 2) they showed an appreciable rise, up to 25 ng/ml (Heap & Deanesly, 1967).

Independent Regression of Normal and Induced Corpora Lutea in Hysterectomized Guinea-Pigs

“…Many ovaries in this series had normal or degenerating follicles of oestrous size, but from the continued inhibition of ovulation, presumably by progesterone (Deanesly, 1968) and from the mucification of the vaginal epithelium up to 116 days after hysterectomy, it appears that the partially regressed corpora lutea are still secreting progesterone. Alternatively, another progestagen may be produced by the lipid-containing interstitial cells during corpora lutea degeneration, as in the rabbit (Hilliard, Spies & Sawyer, 1968).…”

Oestrogen and Progesterone and the Function of the Corpora Lutea in the Guinea-Pig

“…In intact guinea-pigs, the daily absorption of 5 mg. progesterone from implants appeared to have no effect on the development, size or survival of cyclic corpora lutea, although ovulation was inhibited (Deanesly, 1968). However, changes in luteal function according to the timing of injections of progesterone have been re¬ ported.…”

Influence of ergot alkaloids on pituitary prolactin and prolactin‐dependent processes

“…However, the question is whether in other animals and in man prolactin plays a similar essential role in the process of ova implantation as it does in rats. Two studies have indicated that ergocornine is not effective in inhibiting implantation in rabbits (195) and guinea pigs (196). However, a more recent investigation in sows reported that doses of 125-250 mg. of ergocornine can terminate pseudopregnancy in swine with regression of the corpora lutea and reappearance of estrus (197).…”