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Summary.
Premature oviposition was induced in the coturnix quail by intrauterine injection of prostaglandins, essential fatty acids, dibutyryl cyclic AMP, and human seminal plasma. Aspirin and indomethacin inhibited the response to prostaglandin precursors but not to PGE1. Theophylline potentiated the effect of dibutyryl cyclic AMP and low doses of PGE1 and PGE2. Fowl, turkey, bull, boar, and stallion seminal plasma was ineffective on oviposition and contained only small amounts of prostaglandins as determined by radioimmunoassay. It is suggested that prostaglandins may have a physiological rôle in the regulation of oviposition.
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Summary. Collagenase-dispersed theca cells from the 3rd and 4th largest ovarian follicles (T3) were responsive to LH stimulation of both oestrogen and androstenedione production, whereas theca cells from the largest follicle (T1) failed to respond to the gonadotrophin stimulation. Similarly, 8-bromo cAMP and forskolin were more effective in stimulating oestrogen and androstenedione production in T3 than in T, cells, indicating that post-receptor events were involved in the decreased LH responsiveness of T, cells. The C17–20-lyase activity, as measured by conversion of [3H]17-hydroxyprogesterone to androstenedione, was greatly reduced in T, cells as compared to T3 cells. The results demonstrate that a decrease in C17–20-lyase activity, in addition to a decrease in aromatase activity, contributes to the loss of LH-stimulated steroidogenesis in mature theca cells.
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Summary. The activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase: EC 1.1.1.34) was measured in a microsomal preparation of the granulosa of rapidly growing ovarian follicles of laying hens in the late preovulatory period (2–3 h before expected ovulation). The specific activity of the enzyme was measured in the five largest (F1–F5) preovulatory follicles, F1 being the follicle destined to ovulate first. Enzyme activity increased concomitantly with follicle size. The apparent K m of the enzyme decreased 60–80% from the smallest to the largest preovulatory follicle. There was no significant change in the V max during follicle development. Although our results have demonstrated the presence of HMG/CoA reductase in chicken granulosa cells and the progressive increase of its activity with follicular maturation, the quantitative significance of de-novo synthesized cholesterol as steroid hormone precursor remains to be ascertained.
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Summary. A radiochemical assay was utilized to study the inhibitory effects of clomiphene and tamoxifen on the cholesterol side-chain cleavage enzyme activity in a mitochondrial preparation of granulosa cells isolated from mature ovarian follicles of laying hens. At saturating substrate concentrations, both clomiphene and tamoxifen were able to suppress enzyme activity in a dose-related manner IC50 1·8 × 10−5 m). Double reciprocal plots of kinetic data show that the inhibition is mixed, exhibiting competitive kinetics at low concentrations, whereas at high concentrations, the inhibition is of a non-competitive nature. The competitive inhibition constants as determined from Dixon plots are 2 × 10−55 m for clomiphene and 2·3 × 10−55 m for tamoxifen. It is concluded that, in granulosa cells, clomiphene and tamoxifen directly inhibit the mitochondrial cholesterol side-chain cleavage activity. This inhibition may represent an important aspect of the mode of action of clomiphene and tamoxifen.
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Summary. A single oral dose of indomethacin (25 mg) given 2–4 h before expected oviposition delayed oviposition by about 12 h and suppressed plasma PGE levels by about 90%. Intrauterine injection of PGE-1 (0·2–0·4 μg/hen) to 12 hens pretreated with 25 mg indomethacin induced oviposition in all birds in about 7½ min. Passive immunization with goat antiserum to PGE-1 delayed oviposition (69%) in 4 hens. It is concluded that prostaglandins play a functional role in oviposition.
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Summary. Confluent human endometrial stromal cell cultures were exposed to steroids for up to 72 h and then stimulated with agonists of adenylate cyclase for 60 min. Neither steroid alone or in combination had a significant effect on cyclic AMP production. However, when stromal cell adenylate cyclase was stimulated with a receptor-dependent agonist (prostaglandin E), or with forskolin (which acts at a post-receptor site), progesterone in oestradiol-primed cells markedly enhanced (P < 0·05) the effect of both agonists. The presence of phenol red, a weak oestrogenic compound, in the standard culture medium was sufficient to allow the progesterone effect to be manifest. Moreover, while oestradiol alone had no significant effect on prostaglandin E or forskolin-stimulated cyclic AMP production, the simultaneous exposure of cells to oestradiol and progesterone was the most effective treatment. Short-term incubation (up to 120 min) with progesterone had no effect on agonist-induced cyclic AMP accumulation, indicating that progesterone elicits its effect by the classic nuclear mechanism of action. It is suggested that the potentiation by progesterone of prostaglandin E-promoted production of cyclic AMP represents an important aspect of the functional role progesterone plays in the preparation of the endometrium for implantation.
Keywords: endometrium; stromal cell; prostaglandin E; forskolin; cyclic AMP; man
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Departments of Medicine and Physiology, St Louis University School of Medicine, St Louis, Missouri 63104, and *Department of Poultry Science, University of Missouri, Columbia, Missouri 65201, U.S.A.
(Received 27th January 1975)
It is known that the oxytocin (vasotocin) response in the domestic hen varies during the period of a single egg cycle with a significant increase in sensitivity as the time of spontaneous oviposition approaches (Gilbert, 1971). In this respect, the avian shell gland is similar to the mammalian uterus.
We have reported previously that intrauterine injection of prostaglandins (PG) or essential fatty acids (which may serve as prostaglandin precursors) can induce premature oviposition in the domestic fowl (Hertelendy et al., 1974) and the japanese quail (Hertelendy, 1972, 1974). In these studies premature oviposition was induced when there was a hard egg in the uterus, but several hours before the anticipated spontaneous oviposition. The present report is of the response
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The aim of this study was to produce viable chicks by in vitro fertilization and transfer of fertilized ova to the oviduct of recipient hens. Out of a total of 76 transferred ova, 53 were laid with fully calcified shells, 31 of which were fertile (58%). Despite the high rate of embryonic loss, six live chicks were hatched from 12 fertile ova exposed to 0.05 ml of semen (1:200 dilution). Nine healthy chicks were hatched from ten control ova which were recovered from the oviduct following artificial insemination and subsequent transfer to recipient hens. This experimental approach provides a useful model for production of transgenic chicks.
