It is well known that the activity, and response to drugs, of uterine muscle may alter with the reproductive condition of the animal. In a number of species there is, for instance, the phenomenon of reversal of the action of adrenaline, which, whilst it relaxes the non-pregnant uterus, in pregnancy causes contraction. It is not always clear from the literature whether the ovaries of the nonpregnant animals investigated contained corpora lutea. Certainly pregnancy is not always normally necessary for such a reversal; in the cow Cupps & Asdell (1944) found this reversal within the oestrous cycle.On the sheep uterus little work seems to have been done. Polovceva (1940) has made in vivo recordings from non-pregnant animals and found the strength of contractions greatly increased at the time of heat, and their frequency diminished. Recently Gunn (1944) has observed, in vitro, that adrenaline is motox to the non-pregnant uterus of the sheep but inhibitory at the time of parturition-a reversal in the opposite sense to those previously known.The results presented here coh2ern the spontaneous activity in vitro, and the responses to acetylcholine, adrenaline and posterior pituitary extract, of uteri from a number of ewes killed at various stages of pregnancy, and also from a few non-pregnant animals-some normal, other § previously treated with pregnant mare serum gonadotrophin or stilboestrol. It ias been found that the action of oxytocin is prolonged during pregnancy in that it is followed (a) by the appearance of characteristic 'slow' rhythmic contractions which may persist for as long as 1 hr. after the drug is washed out and which resemble the type of activity exhibited by strips of parturient uteri, and (E) by the potentiation of subsequent doses of acetylcholine. It is also shown that the action of adrenaline in pregnancy is a mixture of motor and inhibitory effects and that the inhibitory after-effects may depress the response to other motor drugs.
Quantitative data are given of the anti-oestrogenic action of progesterone on the vulva of the normal oestrous ferret, and the o\l=o"\phorectomized animal treated with oestrogen implants. Initial experiments that suggested a similar action of androstenedione, such as has been reported on the mouse vagina, were not confirmed.Amounts of androstenedione at least 80 times as great as those of progesterone that were effective in collapsing the normal oestrous vulva, and at least 10 times as great as those that antagonized the effect of oestrogen on the vulva and vaginal smear of the castrate, produced no effect.In view of the different method of administration, among other factors, exact equality of relative anti-oestrogenic potency in mouse and ferret was not to be expected; but the observed difference suggests that androstenedione may be metabolized differently in the two species, the metabolites varying in anti-oestrogenic action.It has been shown [Marshall & Hammond, 1945] that progesterone treatment will cause subsidence of the greatly swollen vulva of the oestrous ferret. In the intact animal this effect may possibly be indirect, by suppression of oestrogen secretion. A direct anti-oestrogenic action of progesterone on the ferret vulva was demonstrated by treatment of oöphorectomized animals in which swelling had been induced by the implantation of oestrogen (stilboestrol dipalmitate). Robson [1938] examined the capacity of a number of compounds, including pro¬ gesterone and androstenedione, (a) to inhibit the vaginal cycle in normal mice, and (6) to inhibit vaginal cornification in oöphorectomized mice treated with oestrone. He administered the substances by injection in oil, and found, weight for weight, that androstenedione was nearly as effective as progesterone.It was thought of interest to make a quantitative comparison of the two substances with the ferret vulva-a different species, and a different test organ. The substances were administered by tablet implantation, in view of the time required for the vulva to react, and because the method may be both a more economical and more 'physio¬ logical' one than that of repeated injections. MATERIAL AND METHODSThe ferrets were kept in separate cages, and observations were made on the size of the vulva at least once weekly throughout the year. During periods of treatment records were taken two or three times weekly. The size of the vulva changes relatively slowly, and more frequent inspection does not make for easier detection of a change. Vaginal smears were also taken from a few animals at 2-3-day intervals. A moist cotton-wool swab held on fine forceps was used.Tablets were implanted, under ether anaesthesia, in the fascia immediately below the dense subcutaneous fat of the flank. Care was taken to see that the tablets were well separated when more than one was implanted.
Longissimus dorsi muscles from intact and castrated male ferrets were investigated at the time of maximum body weight in winter, and muscles from control and progesterone-treated animals in summer. The animals had free access to food throughout. The seasonal decrease in body weight was accompanied by decreased fat concentration in the muscle and by reduction of the subcutaneous and mesenteric fat depots. Implantation of progesterone pellets increased the body and muscle weights of intact males (but not of castrated animals) and also increased intramuscular fat. It may have reversed the seasonal pattern of changes in that the fat in the muscle became more unsaturated. The water content of the muscle decreased only reciprocally in relation to the increased fat content. Progesterone had no obvious effect on the composition of muscle in castrated ferrets.In summer the castrated animals had more intramuscular fat than the intact males at this time; moreover, despite the higher concentration, its degree of unsaturation was greater.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.