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Synthetic and natural antiuterotrophic and uterotrophic compounds were tested invitro in their ability to bind to the uterine cytosol receptor for estradiol (Rc) and to favor the formation of the nuclear receptor. These compounds were compared to estradiol in their capacity to decrease the number of specifically bound estradiol in cytosol and increase those in nuclear extracts when incubated with uteri invitro. For each compound, a ‘nuclear transfer activity’ was defined and compared on the one hand to its binding affinity for Rc and on the other hand to its invivo uterotrophic activity. For estrogens devoided of antiestrogenic activity, estradiol and estrone, the nuclear transfer activity was parallel to the affinity for Re and the biological activity. The antiestrogen nafoxidine (U11,100) when added to the cytosol was found to be a reversible and competitive inhibitor of estradiol for Re with an affinity about 30-fold less than estradiol (Ki 7 nM). A complete inhibition could be obtained both before and after the dissociation of Rc by KCl. However, these binding properties of nafoxidine were not in agreement with its partial nuclear transfer activity and its partial uterotrophic activity. The androgens do not bind to Rc; however, they were shown to activate the transfer of the estrogen Rc to the nucleus whereas progesterone did not. These results are discussed in relation to the mechanism of action of uterotrophic and antiuterotrophic compounds.

Summary. Two series of experiments with the isolated perfused rat pancreas were performed in parallel. The conditions differed only with respect to temperature, which was 37.5 ~ in one series and 28 ~ in the other. The lowering of the temperature decreased insulin secretion induced by glucose as well as the insulin response to tolbutamide and acetylcholine. Unlike insulin, glucagon secretion was not significantly modified by hypothermia. Our results suggest that the mechanisms involved in glucagon and insulin secretion are different.Key words: Hypothermia, temperature, insulin release, glucagon release, isolated perfused rat pancreas, glucose, acetylcholine, tolbutamide, arginine.Hypothermia has been shown to inhibit insulin release from the isolated perfused rat pancreas [3]. Our work was undertaken to study simultaneously the effect of hypothermia on insulin and glucagon secretion. The selected temperature was 28 ~ in order to remain within the temperature range compatible with life in homeothermic animals. To our knowledge no other study has examined the effect of low temperature on glucagon secretion in vitro. Materials and MethodsThe pancreas was taken from Wistar rats weighing about 350 g and fed ad libitum. The animals were anaesthetized with sodium pentobarbital, and the pancreas isolated and perfused as previously described [11]. In our preparation the pancreas was isolated from all neighbouring tissues and organs, particularly from the spleen, stomach and duodenum.1 Equipe de Recherche Associ6e au CNRS n ~ 786The perfusion medium was a Krebs-Ringer bicarbonate buffer containing purified bovine albumin (2 g/l) and glucose at different concentrations (0 to 3 g/l). A mixture of oxygen (93%) and carbon dioxide (7%) was bubbled through the medium at atmospheric pressure. The pH of the solution was about 7.3 (range 7.27-7.34).Two experiments were performed in parallel on the same day and the experimental conditions differed only with respect to temperature. The pancreas and the perfusion fluid were maintained at 37.5 ~ or at 28 ~ The flow rate was about 2.4 ml/min (range 2.2-2.6). The arterial perfusion pressure was on average 35 cm H20 (range 31-40) at 37.5 ~ In the experiments at 28 ~ it was on average 2.5 cm higher (range 33-43).In all experiments there was an equilibration period of 30 min. At the end of this period the first sample used for insulin and glucagon assays was collected. In the Figures, time is counted from the beginning of organ perfusion.Insulin was assayed in the effluent from the pancreas using the radioimmunological method B of Hales and Randle [8], with pure rat insulin from Novo Laboratories as the standard.Glucagon was assayed according to the radioimmunological method of Unger et al.[14] using a specific antibody for pancreatic glucagon (30 K of Unger)~ Pork glucagon (Novo) was used as standard. Results, expressed in ng-equivalent, indicate the concentrations of pork glucagon which, within this system, are immunologically equivalent to rat glucagon concentrations in the assay.Variou...

Immature rat uteri contain specific binding proteins for both estradiol and testosterone. In an attempt to compare these two hormonal sites and to determine their localisation, the following was successively established.1. Testosterone did not compete with [3H]estradiol (3 nM) for the estrogen receptor sites, whereas high concentrations of estradiol did compete with [3H]tcstosterone on the androgen receptor.2. After incubation of uteri at low physiological concentration of testosterone, the majority of the testosterone receptor sites was localised in the nucleus, whereas the estradiol receptor sites were found in the cytosol fraction. For higher concentration ( 2 100 nM) of testosterone the two steroid receptor sites were mainly present in the nuclear fraction.3. The complexes of [3H]testosterone and [14C]estradiol with cytosol receptors, when simultaneously prepared and analysed, were shown to behave differently after sucrose-gradient ultracentrifugation and Sepharose chromatography.These results strongly suggest that the receptor sites for testosterone and estradiol in rat uterus are localised on two diffcrent multi-unit proteins in which the steroid binding units are different.The respective roles of estrogen and androgens in rat uterus are not well established, neither is the mechanism by which testosterone modulates the uterotrophic effect of estradiol. The uterotrophic activity of high concentration of testosterone [l] does not seem to be mediated by a transformation into estrogen [2]. Since a testosterone receptor has been demonstrated in rat uterus [3,4], it was thought to be of interest in the understanding of the mechanism of action of testosterone in uterus to determine the relationship between the estrogen receptor and the Trivial Numes. Testosterone, 17[~-hydroxy-3-oxo-androsta-4-ene; estradiol, 3,17a-dihydroxyestra-I ,3,5( 10)-triene; dihydrotestosterone, 17fi-hydroxy-(5a)-androsta-2-ene; dehydroepiandrosterone, 3/J'-hydroxy-17-oxoandrosta-5-ene; androstenedione, 3,17-dioxoandrosta-4-ene ; progesterone, 3,20-dioxopregna-4-ene; cortisol, 1 lp, 17a, 21-trihydroxy-3,20-dioxopregna-4-ene; cyproterone, 6-chloro-17cc-hydroxy-l,2cc-methylene-4,6-pregna-diene-3,20-dione; cyproterone acetate, 6-chloro-1 7cc-acetoxy- testosterone receptor. The two receptor sites displayed different properties, no competition having been observed between testosterone and estradiol on the estrogen receptor [5]. But nothing was known concerning the relationship between the proteins supporting these binding sites. Since the physicochemical properties of the complexes of [3H]testosterone [4] and [3H]estradiol with receptor [6] separately studied after sucrose-gradient centrifugation and gel-filtration chromatography appeared very similar, the question was raised whether the two binding sites were separately localised on a same protein. This hypothesis was strengthened by the observation that treatment of uteri with testosterone in vitro could induce the nuclear localisation of the estrogen receptor sites [7], a fact which did n...