Browsing by Author "FUENTEALBA, B"

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    ESTROGEN AND PROGESTERONE RECEPTORS IN THE OVIDUCT DURING EGG TRANSPORT IN CYCLIC AND PREGNANT RATS
    (1988) FUENTEALBA, B; NIETO, M; CROXATTO, HB
    We investigated the temporal relationships between ovum transport and changes in the concentration of nuclear steroid receptors in the oviduct of cyclic and pregnant rats. A lack of parallelism between estrogen and progesterone fluctuations in plasma and their respective nuclear receptor concentrations in the oviduct predominated during egg transport. In pregnant animals, oviductal egg transport took 24 h longer than in nonpregnant animals. In both conditions, transport was initiated while the action of estrogen and progesterone on the oviduct.sbd.measured as nuclear receptor accumulation.sbd.was decreasing. Three or four days later, depending on whether the animal was pregnant, the eggs entered the uterus shortly after an increase in the nuclear receptor accumulation of both hormones. Treatment with RU486, a progesterone receptor-blocking agent known to cause premature arrival of eggs in the uterus, advanced estrogen receptor accumulation in the oviduct of pregnant rats. These data suggest that the arrival of eggs in the uterus is timed by a transitory increase in nuclear estrogen receptor in the oviduct that does not necessarily reflect a similar change of circulating estradiol. Moreover, in pregnant rats, the onset of this estrogenic action is delayed by a progesterone receptor-mediated effect that hinders nuclear estrogen receptor accumulation.
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    FOLLICLE-STIMULATING HORMONE-GRANULOSA CELL AXIS INVOLVEMENT IN THE ANTIFOLLICULOTROPHIC EFFECT OF LOW-DOSE MIFEPRISTONE (RU486)
    (OXFORD UNIV PRESS UNITED KINGDOM, 1995) CROXATTO, HB; SALVATIERRA, AM; FUENTEALBA, B; LEIVA, L
    This study was designed to assess the involvement of follicle stimulating hormone (FSH)-granulosa and luteinizing hormone (LH)-theca axes in the antifolliculotrophic effect of mifepristone. Plasma gonadotrophins, including plasma LH bioactivity and pulsatility, oestradiol, testosterone and inhibin concentrations, and follicular growth were monitored in volunteer women treated with placebo or mifepristone in two consecutive cycles. Mifepristone was given either as a single dose of 5 mg (n = 7) when the leading follicle had reached a diameter between 12 and 14 mm, or as a multiple dose of 5 mg/day for 3 days, beginning when the leading follicle had reached a diameter between 14 and 16 mm (n = 5) or between 6 and 11 mm (n = 5), Following the single dose of mifepristone, follicular growth and the accompanying increase in plasma oestradiol were arrested at 12 and 36 h respectively without changes in gonadotrophin or testosterone serum concentrations. The 3 day regimen arrested follicular growth and oestradiol rise and decreased plasma inhibin concentrations when follicles were larger than 12 mm at the onset of treatment. These results indicate that the antifolliculotrophic action of mifepristone is associated with a selective compromise of the FSH-granulosa axis of dominant follicles that have passed a critical stage of growth.
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    RELEASE OF H-3 NORADRENALINE FROM THE RAT OVIDUCT - CHANGES DURING ESTROUS-CYCLE AND BY PROGESTERONE INVITRO
    (1990) CHIAPPE, P; GALLEGUILLOS, X; LARA, H; FUENTEALBA, B; FORRAY, I; BELMAR, J
    Rat oviduct noradrenergic innervation seems to be under the influence of hormonal modulation. Noradrenaline level is specifically affected, but other processes like the release of the neurotransmitter have not yet been studied. In this work the release of 3H-noradrenaline (3H-NA) during the estrous cycle and its modification by progesterone "in vitro", were studied. The basal 3H-NA outflow was unchanged during the estrous cycle. However, the induced release (K+, 80 mM) was maximal during estrous. After progesterone, induced 3H-NA release was inhibited at low concentrations (5 .mu.M); under higher concentrations (50 .mu.M) the effect persisted but basal outflow of radioactivity was increased. The inhibitory effect was potentiated by RU-486 (Progesterone blocker). Results suggest a modulatory role for the hormone and it could be related to interactions with nerve-ending membranes and not with classical nuclear receptors.