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ABSTRACT
The effects of hysterectomy and ovariectomy on plasma concentrations of GH, somatomedin A, TSH and thyroxine (T4) were studied in developing rats. Four groups of 24-day-old rats were ovariectomized, ovohysterectomized, hysterectomized or sham-operated. Their weights, lengths and plasma hormone concentrations were measured at 26, 43, 64, 78 and 92 days of age to investigate pre- and postpubertal differences caused by the uterus or ovaries. Plasma concentrations of the hormones examined showed a successive rise with time, but GH and somatomedin A concentrations rose mainly after the opening of the vagina (days 50–55). Higher GH and somatomedin A concentrations were found in the plasma of ovariectomized animals than in ovohysterectomized controls before puberty (GH: 260–300%, P<0·01; somatomedin A: 25–30%, P<0·05). Ovariectomized animals weighed more than ovohysterectomized females after puberty (4·5–6%, P<0·01). This indicated that the uterus exerted a stimulatory effect on GH-somatomedin A regulation and body weight gain in the absence of the ovaries.
Significantly lower plasma somatomedin A (but not GH) concentrations were found in hysterectomized and sham-operated animals than in their respective controls after puberty (30–39%, P<0·01) and their final body weight was lower (22–26%, P<0·001). There were no consecutive uterus- or ovary-related changes in plasma TSH and T4 levels.
It was concluded that both the uterus and ovaries had significant as well as opposite effects on somatomedin A and body weight with the effects of the ovaries being greater than those of the uterus.
J. Endocr. (1987) 113, 21–26
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ABSTRACT
The role of oestradiol-17β in the induction of specific cytosolic receptors for 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) was examined in the immature rat uterus.
An acrylamide gel electrophoretic analysis was developed to separate the specific receptor for 1,25(OH)2D3 from the plasma binding protein for vitamin D3 metabolites. Employing this sensitive method the presence of receptors for 1,25(OH)2D3 in the mature rat uterus was evident. Such receptors were not found in the uterus of saline-treated immature rats. However, oestradiol administration caused an induction of these receptors in the immature rat uterus, together with a significant increase in the uterine weight, progesterone receptor level and peroxidase activity.
These results suggest a mechanism for oestradiol regulation of calcium metabolism in the uterus at times of high demand for this cation during the gestation period.
J. Endocr. (1984) 100, 265–269
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Abstract
Oxytocin (OT) is a neurohypophysial hormone with potent stimulating activity of the pregnant uterus, but its physiological role in parturition is still unclear. Recently, OT was found to be synthesized in the pregnant uterus, indicating that OT originating from the uterus, not from the posterior pituitary gland, may trigger the onset of labour. In order to define the factors responsible for the induction of uterine OT, the effect of ovarian steroid hormones and conceptus on the induction of OT mRNA in the rat uterus was examined by Northern and dot blot hybridization analysis. OT mRNA in the uterus started to increase on day 14 of pregnancy and showed very high levels at the time of parturition. Uterine OT mRNA was not altered by any steroid treatment, oestradiol-17β (0·2 μg), progesterone (4 mg) or both in combination, for 6 days. The gravid horn of the uterus had 3·6-fold as much OT mRNA as the non-gravid horn on day 21 of pregnancy in hemipregnant rats with one ligated oviduct. The ovarian steroid hormones could not induce accumulation of OT mRNA in the uterus of ovariectomized rats, at least under the conditions used, but the presence of a conceptus may be critical for the very high levels of OT mRNA.
Journal of Endocrinology (1995) 146, 81–85
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Search for other papers by H. P. ZASSENHAUS in
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Department of Veterinary Physiology and Pharmacology, Ohio State University, 1900 Coffey Road, Columbus, Ohio 43210, U.S.A.
(Received 30 June 1976)
A possible direct effect of prolactin on the uterus has been proposed by some workers (Leung & Sasaki, 1973; Joseph & Mubako, 1975). In-vitro studies (Leung & Sasaki, 1973) demonstrated that prolactin facilitated the uptake of [3H] oestradiol into uterine tissue. Whether this is due to a specific increase in oestradiol receptors in uterine tissue or to some other mechanism has not been clarified. To examine the in-vivo effects of prolactin on the specific oestradiol receptors in the uterus we designed the following experiments.
Adult female Sprague-Dawley rats (weighing 150-170 g) were ovariectomized. Ovine prolactin (Sigma Chemical Co.) was dissolved in physiological saline and injected (1 mg in 0·1 ml saline) once (morning) or twice (morning and afternoon) daily. In Expt 1, prolactin was injected once daily for 5 days
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The mechanism of action of the uterus on the corpus luteum of the rat is still incompletely understood. Silbiger & Rothchild (1963) suggested that hysterectomy reduced the luteolytic effect of luteinizing hormone (LH) (Rothchild, 1965a) by reducing its secretion, but Christian, Yuan & Rothchild (1968) failed to demonstrate any difference in parameters of LH secretion between intact and hysterectomized pseudopregnant rats. It seemed worth-while, therefore, to test the possibility that the luteolytic action of LH depended on the presence of the uterus.
Regularly cyclic adult Sprague-Dawley rats (200–250 g) were hysterectomized or sham-hysterectomized; a few weeks later, each rat was hypophysectomized and its pituitary transplanted beneath its left kidney capsule. (The corpora lutea, in this preparation, remain functional for several months (Everett, 1956; Rothchild, 1965b).)
Fourteen days later, both the hysterectomized and the sham-hysterectomized rats were divided into two groups: one was injected with 0·9% NaCl solution, the
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SUMMARY
Estimates were made of the number and distribution of cells undergoing division in the mouse uterus during the first 6 days of pregnancy. There was a spectacular change in the distribution of mitoses between days 3 and 4. On day 3 large numbers of mitoses were present in the luminal and glandular epithelium, with few in the stroma, whereas on days 4 and 5 very large numbers were present in the stroma with few in the epithelia.
On day 6 and late on day 5, in the vicinity of a blastocyst, the area containing decidual cells was free of mitoses. Many mitoses were found in the stroma immediately outside this area and there was evidence that the rate of division here was greater than in segments of the uterus unstimulated by a blastocyst.
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SUMMARY
The release of prostaglandin-like material and the spontaneous contractions of individual horns from the pregnant rat uterus in vitro have been studied on day 22 of pregnancy – the expected day of delivery. Removal of foetuses (retaining placentae in utero) from one or both uterine horns on day 16 or 17 significantly reduced prostaglandin F release and spontaneous activity. Rats which had been made unilaterally pregnant after ligation of one uterine horn, exhibited a decrease in prostaglandin F output from both horns. Uterine activity and prostaglandin release were increased in quiescent uteri by the addition of arachidonic acid (5 μg/ml) or phospholipase A (160 mu./ml); these effects were abolished by indomethacin (20 μg/ml). However, the stimulation of uterine activity by PGF2α (30–60 ng/ml) was not affected by indomethacin. It is concluded that the release of prostaglandins from the pregnant rat uterus in vitro at term is related to the presence of viable foetuses.
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SUMMARY
The effects of oestriol, oestradiol and oestrone on the uterus and vagina of the mouse have been investigated, by measuring changes in the incorporation of tritiated uridine into RNA, and in wet and dry organ weight. The time course of the uridine response to a single injection of oestriol differs markedly from that seen with single injections of oestradiol and oestrone. Oestriol has only a weak uterotrophic action in tests employing daily oestrogen injections, but when administered every 4 hr. in small doses it elicits as much growth in both organs as does oestradiol. The relative capacities of oestriol and oestradiol to sensitize the uterus to the induction of deciduomata by peanut oil are contrasted.
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The transport of 131I-labelled polymer microspheres through the female reproductive tract of the rabbit has already been reported (Glover & Patterson, 1963; Glover & Wood, 1964), but the systemic distribution of residual unbound radioactive iodide after the process of labelling the microspheres has not been described in detail. This information is needed, however, in order to distinguish radioactivity in the uterus which is bound to the microspheres from that which arises from unbound radioactive iodide. The level of radioactivity found in the uterus after administration of suitable quantities of 131I as sodium iodide has therefore been determined.
Twenty-one oestrous rabbits received 1–5 μc Na131I. Of these, ten were injected intravenously, and in 11 the iodide was deposited in the anterior vagina. The animals were killed by i.v. injection with sodium pentobarbitone, 3 gr./ml., (Euthatal, May and Baker Ltd.) after 3, 6 or 12 hr. and their
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This investigation stems from two papers by Rudzik & Miller (1962a, b) on the mechanism by which relaxin effects uterine myometrial inhibition. From the results of experiments in vitro, the authors concluded that, in the rat, the uterine inhibitory action of relaxin is mediated indirectly through the release of catecholamines, mainly adrenaline. Relaxin also inhibits uterine contractions in the mouse. A number of experiments on the mouse uterus in vitro have been carried out in this laboratory by Mr P. A. Judd (unpublished). Although more work needs to be done before Rudzik & Miller's hypothesis can be accepted for this species, the preliminary results are, in the main, similar to those reported for the rat.
The experiments of Rudzik & Miller give no clue to the site of storage and release of adrenaline in the uterus, but the authors point out that Adams-Ray, Nordenstam & Rhodin (1958) reported the
