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M. C. SHELESNYAK and G. J. MARCUS

Recently, in a brief communication, Coppola, Ball & Brown (1966) reported an incidence of 17% spontaneous deciduomata in pseudopregnant rats. One to three discrete zones of decidualization per uterus were observed. One of us, (M.C.S.), who has been concerned with the problem of decidualization for many years, has never observed as high an incidence of spontaneous decidualization. Because of the importance of the decidual response and decidual induction as a model system in the study of nidation (Shelesnyak, 1957) and of mammalian tissue growth and differentiation (Shelesnyak, 1962), it is essential to have a reliable index of the efficiency, or lack thereof, in induction of the decidual response under experimental conditions. Any degree of spontaneous decidualization would decrease the reliability of the experimental system by making unreliable such usual criteria as the weight of

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P. F. KRAICER and M. C. SHELESNYAK

Summary.

Impregnated rats were given a subcutaneous injection of ergocornine methanesulphonate between 0·15 and 0·5 mg/rat on the 4th day of gestation. The earliest response studied was the appearance of the oestrous vaginal smear, 2 to 3 days after drug injection. Gestation was terminated in three-quarters of the rats exhibiting vaginal oestrus. The ED50 for induction of oestrus and for termination of pregnancy was approximately 0·3 mg. Following the ergocornine-induced oestrus, the minority of rats exhibited normal oestrous cycles. Most rats had a spontaneous pseudopregnancy. During this pseudopregnancy, deciduomata could be elicited by `physiological' means, i.e. systemic histamine release. The weight of these deciduomata was, however, somewhat depressed. It is pointed out that a single injection of the drug elicits a complex series of endocrine sequelae.

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E. S. KISCH and M. C. SHELESNYAK

Summary.

An attempt was made to test whether modification of the ergocornine molecule (eco) by the liver is a prerequisite to its pregnancyinterrupting action, and whether the liver plays a role in the elimination of the drug from the organism. For this purpose eco was administered to the perfused rat liver and into the portal bed of the pregnant rat. The effectiveness of the drug in terminating progestation when administered by these routes was less than one-fourth the effectiveness following systemic injections. Attempts to recover biologically active eco from the bile and the liver itself failed. This suggests inactivation of the ergot alkaloid by the liver.

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E. S. KISCH and M. C. SHELESNYAK

Summary.

A single administration of ergocornine methanesulphonate (eco) interrupts pregnancy of the rat when given on any day until the 7th after coitus, but not later. The drug also interrupts pseudopregnancy at any time during its course, without temporal limitation. The failure of eco to interfere with pregnancy is correlated with the presence and endocrine activity of an implanted conceptus.

The factors causing failure of eco to interfere with gestation after implantation were identified by a series of successive steps : (1) The presence of deciduomata—thought to be analogous to maternal decidual tissue—in the pseudopregnant uterus was shown not to oppose eco action. (2) Animals, whose foetuses have been removed, leaving only maternal and foetal placenta in situ, were protected against the action of eco. Thus, this implicated by elimination the foetal placenta as causing failure of eco action in pregnancy after the 7th day. Indeed, placental grafts from late pregnant donors could be shown to overcome eco action even in this first 7-day period.

As early as the 10th day, a luteotrophic influence was present in placental extracts, as measured by prevention of eco action on pregnancy. In the literature, a luteotrophic influence is attributed to (foetal) placental tissue. The failure of eco to interrupt pregnancy by the 8th day is taken as indication of placental luteotrophic activity at that time, i.e. 3 days before it can be detected when hypophysectomized rats are used for this purpose.

The action of eco is considered as mediated by pituitary lth depression. Thus, the use of this drug allows suppression of lth without performing hypophysectomy. Placental luteotrophin is not affected by eco.

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M. C. SHELESNYAK and P. F. KRAICER

Summary.

A method is described for inducing decidualization of the uterus of the pseudopregnant rat, which is based on the utilization of systemically released histamine. Although per os, subcutaneous, intraperitoneal, intravenous and intracardiac routes can be used, the most generally effective is intraperitoneal. A single injection of pyrathiazine hydrochloride (Pyrrolazote, Upjohn) as 1 ml of 0·06 m aqueous solution (2% w/v), administered at 1000 hr on the 4th day of dioestrus of pseudopregnancy, was effective in inducing extensive decidualization of the endometrium.

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M. C. SHELESNYAK and P. F. KRAICER

Summary.

To study the duration of inhibition of decidual induction by intrauterine antihistamine, 163 rats were made pseudopregnant immediately after experiencing two consecutive normal oestrous cycles. Decidualization was induced by systemic injection of histamine releaser on 4th day of dioestrous state of pseudopregnancy (L4). Antihistamine (as inhibitor of decidual induction) was instilled unilaterally into uteri of groups of rats, on each of the 14 days (2×4 days of oestrous cycles plus pro-oestrus, oestrus and first 4 days of leucocytic phase of pseudopregnancy). Practically no decidual response was elicited when inhibition treatment was administered during pseudopregnancy; earlier administration resulted in partial inhibition of response.

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BERTHA L. LOBEL, M. C. SHELESNYAK and LILIANE TIC

Summary.

When pregnant rats are given a single subcutaneous injection of ergocornine methanesulphonate on the 4th day of gestation, physiological indications of changes in the ovary are manifold.

Activities of a number of histochemically demonstrable enzymes were investigated in the ovaries of ergot-treated pregnant rats. The enzymes included Δ5-3β-hydroxysteroid dehydrogenase, succinic dehydrogenase, alkaline and acid phosphatase and adenosine-triphosphatase.

The ovaries were examined at 2-, 4-, 8- and 24-hr intervals after administration of the drug. Macroscopic and microscopic vascular dilatation and engorgement were seen in the ovaries at 2, 4 and 8 hr and had decreased by 24 hr. Activities of Δ5-3β-hydroxysteroid dehydrogenase and succinic dehydrogenase were histochemically demonstrable in the corpora lutea of gestation as well as other sites in the ovary at 2, 4 and 8 hr after ergocornine. At 24 hr, portions of the corpora lutea of gestation showed necrosis and dissolution of cells and many healthy vesicular follicles had developed. These changes in the ovary (luteolysis in the corpora lutea of gestation and development of follicles to the ovulation stage) form the basis for the physiological effects—interruption of gestation and appearance of oestrus—which occur 2 to 3 days after administration of ergocornine to pregnant rats during progestation.

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G. J. MARCUS, P. F. KRAICER and M. C. SHELESNYAK

Summary.

A single intraperitoneal injection of pyrathiazine induces extensive decidualization of the progravid uterus of the rat. This action was considered to be mediated by the release of histamine. The present study was undertaken to show that pyrathiazine, an antihistaminic drug, causes histamine release.

Injection of pyrathiazine in rats produced a characteristic histaminerelease syndrome, and caused a twofold increase in the urinary excretion of histamine. Pretreatment with pyrathiazine protected rats from the lethal effects of challenge doses of histamine-liberator Compound 48/80 but not of histamine.

These actions of pyrathiazine demonstrate that it releases histamine in the rat, and that its effectiveness as a decidual inducer is consistent with the postulated role of histamine in decidual induction.

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P. F. KRAICER, G. J. MARCUS and M. C. SHELESNYAK

Summary.

Pregnant and pseudopregnant rats were depleted of histamine by treatment with histamine liberator Compound 48/80 or pyrathiazine. The response to decidual induction by systemic histamine release was compared with the response to direct stimulation of the endometrium. The decidual reaction in response to endometrial trauma and to the presence of ova was markedly reduced, whereas systemic induction with pyrathiazine could be prevented completely. These observations support the hypothesis that induction of decidualization by systemic pyrathiazine is mediated by the release of histamine systemically, whereas induction by local stimuli is mediated by release of uterine histamine only.

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PUTTIPONGSE VARAVUDHI, BERTHA L. LOBEL and M. C. SHELESNYAK

Summary.

Successful induction of decidualization on the 4th day of pseudopregnancy (L4) is possible in rats hypophysectomized on L3 of pseudopregnancy (after 19.00 hours). However, in the absence of exogenous hormone, the decidual cell reaction cannot be maintained in the hypophysectomized rat. The effect of hypophysectomy on decidualization which is already established depends upon the time of removal of the pituitary. When hypophysectomy was performed before the 11th day of pseudopregnancy (L11) breakdown and resorption of the deciduomata occurred within 4 days; when hypophysectomy was carried out on L11 or L12, the deciduomata were resorbed more slowly. This relatively prolonged resorption was related to the absence of ovulation at the end of the period of pseudopregnancy in the hypophysectomized rats. The results indicate that no luteotrophic factor of uterine or decidual origin is produced in the pseudopregnant rat bearing deciduomata.