Category Archives: Steroid Hormones

Local Release of Steroid Hormones: DISCUSSION(5)

TNFa and IL-1p were shown to stimulate P4 secretion in the isolated rat ovary perfused in vitro and in a rat follicle culture, whereas they did not exert any clear effect on basal or LH-stimulated P4 production in the present MDS study. Our data are partly comparable with the results of a study of porcine theca cells in which TNF-a did not affect basal secretion of P4 from the cells but caused a marked dose-dependent inhibition of LH-stimu-lated P4 production. As the present data are the first on the effects of cytokines in an MDS study in the bovine follicle, a detailed evaluation of these effects must await an accumulation of data from different systems of bovine follicles, rather than from other species.

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Local Release of Steroid Hormones: DISCUSSION(4)

DISCUSSION(4)

ET-1 affected steroidogenesis in the present MDS study. A previous study using a rat granulosa cell culture showed a direct action of ET-1 on steroidogenesis. This action involves selective modulation of key steroidogenic steps concerned with formation and degradation of steroids: ET-1 attenuates enzymatic action common to P4 and A production, such as that of cholesterol side-chain cleavage and 3p-hydroxysteroid dehydrogenase (3p-HSD), but increases the activity of those enzymes that participate in their degradation (5a-reductase and 3p-HSD). Indeed, ET-1 also inhibited the release of P4 and A from the bovine ovary in the present MDS study. In contrast, E2 release was stimulated by ET-1 for a prolonged period, suggesting that ET-1 may stimulate aromatase activity. Although the effect of ET-1 on the release of E2 in the MDS might be through an indirect pathway, a direct stimulatory effect of ET-1 on the E2 secretion is also highly possible. ventolin inhaler

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Local Release of Steroid Hormones: DISCUSSION(3)

In the present model, it is likely that an increase of local P4 concentration by LH stimulation accelerates the cascade of steroid biosynthesis and that this influence could overcome the well-known direct inhibitory effect of LH on the E2 secretion, thus resulting in the increase in both A and E2 secretion. Additionally, the present results provide evidence that LH stimulates the release of ET-1 from the theca layer of bovine mature follicles in vitro. Similar findings were shown in a study by Girsh et al. in which LH stimulated the ET-1 content in a bovine corpus luteum slice incubation. The effect may be a direct stimulation of LH on the endothelial cells in the theca layer, since we could not find measurable concentrations of ET-1 in the medium used to culture bovine granulosa and theca cells (unpublished results). To support this hypothesis, mRNA for LH receptor must be detected in endothelial cells in the theca layer, which requires further investigation. buy diabetes drugs

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Local Release of Steroid Hormones: DISCUSSION(2)

DISCUSSION(2)

Microscopic observations, as well as the selective increase of the release of A rather than the release of E2 in response to pregnenolone infusion, confirmed that the MDS capillary membranes were placed in the theca layer, where the predominant secretory product is A. This is further supported by the fact that the basal concentration of A in the perfusate was more than 2-fold higher than that of E2. LH and the peptides infused into the capillary membrane are considered to diffuse along a concentration gradient into the extracellular fluid and modify the cellular secretory function in a paracrine manner. Based on the observation from the preliminary experiment that substances infused in one line did not affect the hormonal release in other lines separated by at least a 5-mm distance, a maximum of four lines per follicle were implanted. The individual response of each line to the infused peptides suggests that the microenvironment of each line was independent from that of other lines. birth control pills

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Local Release of Steroid Hormones: DISCUSSION(1)

The results of the present study demonstrated that mature follicles isolated from the bovine ovary and incubated in an organ culture chamber maintained the ability to produce and release steroids, PGE2, and ET-1 into the MDS implanted in the theca layer throughout the experimental period. To select follicles that were mature, but at a stage before the LH surge, we determined concentrations of steroids, PGE2, and ET-1 in the follicular fluid. PGE2 concentration in the follicular fluid after the endogenous LH surge has been shown to be much higher than that from the pre-LH surge period in the cow. ventolin inhalers

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Local Release of Steroid Hormones: RESULTS(2)

RESULTS(2)

TNFa alone did not affect basal production of P4, A, or E2, but it suppressed the LH-stimulated release of A and E2 (p < 0.05; Fig. 2). IL-1p inhibited the release of A but stimulated the release of E2 (p < 0.05) without having any distinct effect on the release of P4 (Fig. 3). buy levaquin online

Effects of ET-1, TNFa, and IL-1/3 on the Release of PGE2

ET-1, TNFa, and IL-1p stimulated PGE2 release for a prolonged period (p < 0.05; Fig. 4). The infusion of ET-1 or TNFa after LH exposure induced a further increase of PGE2 release as compared with LH infusion alone (p <0.05; Fig. 4).

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Local Release of Steroid Hormones: RESULTS(1)

Effects of LH on the Secretory Function of Mature Follicles

Infusion of LH clearly increased the release of P4, A, E2, and PGE2 (201 ± 15% for P4, 163 ± 9% for A, 186 ± 11% for E2, and 212 ± 12% of baseline for PGE2; mean ± SEM; p < 0.001). The increase in A release was observed only during the LH infusion, while the release of P4 remained at higher levels until 2 h after LH infusion. LH infusion induced increases in the release of both E2 (p < 0.05; Figs. 1-3) and PGE2 (p < 0.05; Fig. 4), and these stimulatory effects were maintained until the end of the experiment. The release of ET-1 was also increased after LH exposure (165 ± 23% of baseline; mean ± SEM; p < 0.05) and remained at high levels until the end of the experiment (p < 0.05; Fig. 5). buy ampicillin

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Local Release of Steroid Hormones: MATERIALS AND METHODS(6)

MATERIALS AND METHODS(6)

The EIA for ET-1 was performed as described previously. The standard curve ranged from 10 to 20 000 pg/ ml. The intra- and interassay CVs were 8.5% and 13.5%, respectively. asthma inhalers

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Local Release of Steroid Hormones: MATERIALS AND METHODS(5)

The EIA for E2 was carried out as described previously. The standard curve ranged from 2 to 2000 pg/ml, and the ED50 of the assay was 120 pg/ml. The intra- and interassay CVs were 6.1% and 8.9%, respectively.

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Local Release of Steroid Hormones: MATERIALS AND METHODS(4)

MATERIALS AND METHODS(4)ET-1 Extraction

After the diethyl ether extraction, the remaining Ringer’s solution was used for ET-1 extraction. BSA was added to the samples to a final concentration of 1 mg/ml. Follicular fluids (2 ml) were diluted with the same volume of distilled water, and the pH was adjusted to 2.5 with acetic acid. The samples were then applied to a Sep-Pak C18 Cartridge (Waters, Millford, MA) as described previously. The residue was evaporated and then dissolved in 200 ^l assay buffer (42 mM Na2HPO4, 8 mM KH2PO4, 20 mM NaCl. 4.8 mM EDTA, 0.05% BSA, pH 7.5) for peptide EIA. Thus, the samples were concentrated about 15-fold as a result of the process. The recovery rate of ET-1 (10 pg/ml) that had been added to the Ringer’s solution was 63%.

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