scholarly journals Demonstration of a non-steroidal, non-inhibin factor in the ovine corpus luteum of pregnancy that reduces pituitary responsiveness to GnRH-induced LH secretion in vitro

Reproduction ◽  
2003 ◽  
pp. 35-42 ◽  
Author(s):  
PA Fowler ◽  
NP Groome ◽  
KH Al-Gubory
Keyword(s):  
Corpus Luteum ◽  
Follicular Fluid ◽  
Corpora Lutea ◽  
Pituitary Cells ◽  
Human Follicular Fluid ◽  
Threefold Increase ◽  
Rat Pituitary ◽  
Rat Pituitary Cells ◽  
Lh Secretion

The decline in pulsatile LH secretion and pituitary responsiveness to GnRH as pregnancy advances may be due to non-steroidal factors secreted by the ovine corpus luteum of pregnancy. Corpora lutea from ten ewes on days 70-80 of gestation were homogenized, charcoal-treated and, together with charcoal-treated follicular fluid from superovulated women, were subjected to inhibin immunoaffinity chromatography, reducing dimeric inhibin A and B by >90% and abolishing inhibin bioactivity. These preparations were investigated using cultures of rat pituitary cells. GnRH-induced LH and FSH secretion in vitro was reduced by ovine corpus luteum extract and human follicular fluid by 47+/-5% and 42+/-5% of control LH and by 37+/-5% and 50+/-10% of control FSH, respectively (P<0.001). Extracts prepared from corpora lutea and placentae that were collected on days 50, 90 and 120 of pregnancy (five ewes per stage of pregnancy) showed increased GnRH-induced LH-suppressing bioactivity, particularly in the case of the placental extracts, with a threefold increase in activity. When partially purified by pseudochromatofocusing, GnRH-induced LH-suppressing bioactivity in extracts of ovine corpora lutea was identified at pH 5.40 and 5.77. Although these values are similar to published gonadotrophin surge-attenuating factor (GnSAF) bioactivity pI values, a GnSAF-blocking antiserum had no consistent effect on ovine corpus luteum extract GnRH-induced LH-suppressing bioactivity. It was concluded that the ovine corpus luteum of pregnancy contains a non-steroidal, non-inhibin factor, probably not GnSAF, that has the ability to reduce pituitary responsiveness to GnRH in vitro.

Higher gonadotrophin surge-attenuating factor bioactivity is found in small follicles from superovulated women

1994 ◽  
Vol 143 (1) ◽  
pp. 33-44 ◽  
Author(s):  
P A Fowler ◽  
M Fraser ◽  
P Cunningham ◽  
P G Knight ◽  
B Byrne ◽  
...  
Keyword(s):  
Inverse Relationship ◽  
Hydrophobic Interaction Chromatography ◽  
Pituitary Cells ◽  
Human Follicular Fluid ◽  
Follicle Diameter ◽  
Rat Pituitary ◽  
Follicle Size ◽  
Rat Pituitary Cells ◽  
Lh Secretion

Abstract Ovine and rat pituitary bioassays for gonadotrophin surgeattenuating factor (GnSAF) were utilized to determine whether the level of GnSAF bioactivity in pooled human follicular fluid (hFF) from superovulated women varied according to follicle diameter (≤11 mm, 12–15 mm and 16–21 mm follicles examined using the ovine bioassay, or ≤10 mm, 11–13 mm, 14–17 mm, 18–20 mm, 21–24 mm and ≥ 25 mm follicles examined using the rat bioassay). When tested using dispersed ovine pituitary cells, GnSAF bioactivity, expressed in terms of the reduction in gonadotrophin-releasing hormone (GnRH)-induced LH secretion, was inversely related to follicle diameter (P<0·01). In response to 5 μl hFF/well from follicles of ≤ 11, 12–15 and 16–21 mm diameter, GnRH-induced LH secretion was reduced to 40·5±6·6.9%, 65·2±6·6% and 83·7±7·9% of control respectively. A similar inverse relationship was observed when a second batch of hFF samples from different sized follicles was tested using rat pituitary cell monolayers. Expressing GnSAF bioactivity in terms of the dose required to suppress GnRH-induced LH secretion by rat pituitary cells to 50% of the maximal suppression observed (ED50), the three smallest follicle size pools contained the most GnSAF (ED50 values of 0·13, 2·79 and 5·36 μl hFF/well from follicles of ≤ 10, 11–13 and 14–17 mm respectively). The ED50 values for follicles of 18–20, 21–24 and ≥25 mm were 8·81, 27·1 and 60·0 μl hFF/well respectively. Thus hFF from follicles ≤ 11 mm was over 450 times more potent than hFF from follicles ≥ 25 mm in suppressing GnRH-induced LH release. The ED50 values for inhibin bioactivity (measured as the suppression of basal FSH secretion from rat pituitary monolayers) were much less variable than those for GnSAF bioactivity (between 0·85 and 0·13 μl hFF/well). Inhibin immunoreactivity, measured by a two-site immunoradiometric assay, followed the same pattern as inhibin bioactivity with lowest concentrations in the smallest follicles (41·96 ng/ml) and highest concentrations in the three largest follicle size groups (56·48–64·48 ng/ml). The specific effects of inhibin on GnRH-induced LH and basal FSH release in these pituitary bioassays were determined by incubating culture dishes with pure recombinant human inhibin at doses of 0·025–25 ng/well. In both the sheep and rat pituitary monolayers, basal FSH was suppressed (ED50=0·02 and 0·16 ng/well respectively). However, while inhibin markedly stimulated GnRH-induced LH secretion from ovine pituitary monolayers (ED50=0·04 ng/well), it suppressed GnRH-induced LH secretion from rat pituitary monolayers (ED50=0·31 ng/well) by 13%. The divergent effects of inhibin on GnRH-induced LH secretion in the two culture systems, and the relative insensitivity of GnRH-induced LH secretion to recombinant human inhibin in the rat system, indicates that the inverse relationship between GnSAF concentrations and follicular diameter cannot be an artefact of inhibin bioactivity. In addition, when hFF was fractionated by hydrophobic interaction chromatography using phenyl Sepharose, fractions which contained the greatest amounts of GnSAF bioactivity differed from those which contained peak levels of bioactive or immunoreactive inhibin. These results support in vivo observations that small follicles are important regulators of gonadotrophin secretion in superovulated women. Concentrations of GnSAF fall as the follicles approach an ovulatory size which enables positive steroid feedback on pituitary responses to hypothalamic GnRH, leading to the preovulatory LH surge. Journal of Endocrinology (1994) 143, 33–44

Leukotriene C4 stimulates LH secretion from rat pituitary cells in vitro

1984 ◽  
Vol 106 (2) ◽  
pp. 459-460 ◽  
Author(s):  
Anna-Lena Hulting ◽  
Jan-Åke Lingren ◽  
Tomas Hökfelt ◽  
Katarina Heidvall ◽  
Peter Eneroth ◽  
...  
Keyword(s):  
Pituitary Cells ◽  
Leukotriene C4 ◽  
Rat Pituitary ◽  
Rat Pituitary Cells ◽  
Lh Secretion

Gonadotrophin surge-attenuating factor attenuates in-vitro LH secretion induced by gonadotrophin-releasing hormone from cultured ovine pituitary cells only during the breeding season

1992 ◽  
Vol 135 (2) ◽  
pp. 221-227 ◽  
Author(s):  
P. A. Fowler ◽  
C. Townsend ◽  
I. E. Messinis ◽  
P. Cunningham ◽  
A. Templeton
Keyword(s):  
Breeding Season ◽  
Follicular Fluid ◽  
Primary Cultures ◽  
Pituitary Cells ◽  
Partial Reduction ◽  
Human Follicular Fluid ◽  
Gonadotrophin Releasing Hormone ◽  
Lh Secretion ◽  
Stimulation Of

ABSTRACT Primary cultures of ovine pituitaries from adult ewes were used to investigate aspects of gonadotrophin surge-attenuating factor (GnSAF) bioactivity in human follicular fluid (hFF) from superovulated women. During the autumn and first half of the winter, LH secretion induced by gonadotrophinreleasing hormone (GnRH) was markedly reduced (43·5 ± 5·2% of control GnRH-induced LH secretion) by incubation for 48 h with steroid-free hFF. For the rest of the year, treatment with the same batch of steroid-free hFF resulted in non-significant reduction or stimulation of GnRH-induced LH secretion (71·3± 13·2 to 117·8±11·2% of control GnRH-induced LH secretion). Incubation of pituitary cells for 48 h with oestradiol (1 pmol/l to 1 μmol/l), progesterone (1 pmol/l to 1 μmol/l) or oestradiol and progesterone combined (1 pmol/l to 1 μmol/l) in a two-way titration for 48 h had no significant effect on GnRH-induced LH secretion (83·4±7·6 to 110·6±5·0% of control secretion). Separating hFF into fractions of different molecular mass by ultrafiltration demonstrated that GnSAF bioactivity was present in a form 10–30 kDa in size. Incubation for 48 h with these fractions had no significant effect on basal FSH secretion but significantly attenuated GnRH-induced LH secretion during the autumn. The same fractions had little effect on GnRH-induced LH secretion from pituitary cells collected during the summer. We conclude that ovine pituitaries display at least partial reduction in sensitivity to GnSAF outside the breeding season. In addition, neither oestradiol nor progesterone singly or in combination caused the observed attenuation of GnRH-induced LH secretion that is ascribed to GnSAF bioactivity. Journal of Endocrinology (1992) 135, 221–227

Action and formation of inositol bisphosphate and inositol trisphosphate in rat anterior pituitary cells

1990 ◽  
Vol 123 (4) ◽  
pp. 459-463 ◽  
Author(s):  
Andrzej F. Przylipiak ◽  
Ludwig Kiesel ◽  
Thomas A. Karenberg ◽  
Maria S. Przylipiak ◽  
Benno Runnebaum
Keyword(s):  
Inositol Phosphates ◽  
Inositol Trisphosphate ◽  
Pituitary Cells ◽  
Permeabilized Cells ◽  
New Findings ◽  
Rat Pituitary ◽  
Lh Release ◽  
Rat Pituitary Cells ◽  
Lh Secretion

Abstract. Inositol 4,5-bisphosphate and inositol 1,4,5-trisphosphate, administered exogenously at a concentration of 3× 10−5 mol/l increased LH release in superfused rat pituitary cells by 950±267% and 281±83%, respectively. This stimulatory effect was reversible and dose-dependent. Other inositol phosphates (inositol 1-monophosphate, inositol 1,4,5,6-tetrakisphosphate, inositol 1,3,4,5,6-pentakisphosphate and inositol 1,2,3,4,5,6-hexakisphosphate), tested in vitro, did not significantly influence LH release. In saponin-permeabilized cells, the rate of basal and stimulated LH release was twice that in non-permeabilized cells. Penetration of inositol bisphosphate and inositol trisphosphate into saponin-treated pituitary cells did not increase the secretory potency of these agents compared with their effect on non-permeabilized cells. The new findings document that inositol trisphosphate formation occurs within 5-45 s after GnRH (10−7 mol/l) administration and seems to be involved in mediating the rapid, first phase of LH release, whereas inositol bisphosphate formation occurs after 3-15 min and is probably related to later phases of LH secretion. Our results suggest that inositol bisphosphate and inositol trisphosphate are important regulators of the release of luteinizing hormone and can exert their effects not only intracellularly, but also extracellularly.

Modulation of prolactin secretion by contraceptive progestins in cultured rat pituitary cells in vitro

1988 ◽  
Vol 117 (4_Suppl) ◽  
pp. S188-S189
Author(s):  
L. KIESEL ◽  
T. RABE ◽  
D. SCHOLZ ◽  
V. KIRSCHNER ◽  
B. RUNNEBAUM
Keyword(s):  
Prolactin Secretion ◽  
Pituitary Cells ◽  
Rat Pituitary ◽  
Rat Pituitary Cells

A COMPARISON OF THE EFFECTS OF FOUR ERGOT DERIVATIVES ON PROLACTIN SECRETION BY DISPERSED RAT PITUITARY CELLS

1980 ◽  
Vol 87 (1) ◽  
pp. 95-103 ◽  
Author(s):  
G. DELITALA ◽  
T. YEO ◽  
ASHLEY GROSSMAN ◽  
N. R. HATHWAY ◽  
G. M. BESSER
Keyword(s):  
Anterior Pituitary ◽  
Ergot Alkaloids ◽  
Prolactin Secretion ◽  
Pituitary Cells ◽  
Inhibitory Effects ◽  
Prolactin Release ◽  
Ergot Derivatives ◽  
Rat Pituitary ◽  
Rat Pituitary Cells

The inhibitory effects of dopamine and various ergot alkaloids on prolactin secretion were studied using continuously perfused columns of dispersed rat anterior pituitary cells. Bromocriptine (5 nmol/l) and lisuride hydrogen maleate (5 nmol/l) both inhibited prolactin secretion, the effects persisting for more than 3 h after the end of the administration of the drugs. A similar although less long-lasting effect was observed with lergotrile (50 nmol/l) and the new ergoline derivative, pergolide (5 nmol/l). These effects contrasted with the rapid disappearance of the action of dopamine. The potency estimates of the ergots relative to that of dopamine were: lergotrile, 2·3; bromocriptine, 13; lisuride, 15; pergolide, 23. The dopamine-receptor blocking drugs, metoclopramide and haloperidol, antagonized the prolactin release-inhibiting activity of the compounds; bromocriptine and lisuride showed the highest resistance to this dopaminergic blockade. The results suggested that the direct effect of the ergot derivatives on dispersed pituitary cells was mediated through dopamine receptors and emphasized the long-lasting action of bromocriptine and lisuride in vitro.

Modulatory effect of steroid hormones on GnRH-induced LH secretion by cultured rat pituitary cells

1992 ◽  
Vol 70 (7) ◽  
pp. 963-969 ◽  
Author(s):  
Gabriela T. Pérez ◽  
Marta E. Apfelbaum
Keyword(s):  
Steroid Hormones ◽  
Pituitary Cells ◽  
Short Term ◽  
Stimulatory Action ◽  
Rat Pituitary ◽  
Lh Release ◽  
Gonadotrophin Releasing Hormone ◽  
Rat Pituitary Cells ◽  
Lh Secretion

The purpose of the present experiments was to examine the short- and long-term effects of estradiol-17β (E2), progesterone (P), and 5α-dihydrotestosterone (DHT), alone and in combination, on the gonadotrophin-releasing hormone (GnRH)-induced luteinizing hormone (LH) secretion, using an ovariectomized rat pituitary cells culture model. After 72 h in steroid-free medium, pituitary cells were further cultured for 24 h in medium with or without E2 (1 nM), P (100 nM), or DHT (10 nM). Cultures were then incubated for 5 h in the absence or presence of 1 nM GnRH with or without steroids. LH was measured in the medium and cell extract by radioimmunoassay. The results show that the steroid hormones exert opposite effects on the release of LH induced by GnRH, which seems to be dependent upon the length of time the pituitary cells have been exposed to the steroids. In fact, short-term (5 h) action of E2 resulted in a partial inhibition (64% of control) of LH release in response to GnRH, while long-term (24 h) exposure enhanced (158%) GnRH-induced LH release. Similar results were obtained with DHT, although the magnitude of the effect was lower than with E2. Conversely, P caused an acute stimulatory action (118%) on the LH released in response to GnRH and a slightly inhibitory effect (90%) after chronic treatment. GnRH-stimulated LH biosynthesis was also influenced by steroid treatment. Significant increases in total (cells plus medium) LH were observed in pituitary cells treated with E2 or DHT. While the stimulatory effect of E2 was evident after both acute (133%) and chronic (119%) treatment, that of DHT appears to be exerted mainly after long-term priming (118%). These results suggest that the steroids modulate GnRH-induced LH secretion by acting on both synthesis and release of LH. On the other hand, total hormone content was not affected by P. The acute (5 h) effects of E2, P, and DHT on the GnRH response in E2-primed (24 h) cells during a short-term incubation, were also tested. Addition of P to the pituitary cells primed with E2 led to an acute potentiation of the stimulatory effect of E2 on GnRH-induced LH release and total content. Conversely, the augmentative E2 effect on pituitary responsiveness to GnRH was abolished by DHT. Taken together, these findings suggest that the physiological significance of the stimulatory action of progesterone could be to define the final magnitude of the LH preovulatory surge, while the inhibition by DHT could be required to limit the LH surge to that day of proestrus.Key words: luteinizing hormone, gonadotrophin-releasing hormone, steroid hormones, cultured pituitary cells.

In vitro evidence of a role for inhibin in female rabbits

1984 ◽  
Vol 246 (3) ◽  
pp. E243-E248
Author(s):  
A. L. Goodman
Keyword(s):  
Granulosa Cells ◽  
Pituitary Cells ◽  
Dependent Manner ◽  
C Cells ◽  
Rat Pituitary ◽  
Reference Preparation ◽  
Lh Release ◽  
Rat Pituitary Cells ◽  
I Cells

To examine a regulatory role for inhibin in female rabbits, an in vitro bioassay for inhibin activity was modified to use cultured rabbit pituitary cells and charcoal-extracted porcine follicular fluid (pFFx) as a reference preparation. pFFx inhibited follicle-stimulating hormone (FSH) release in a dose-dependent manner in cultures from both intact (I) and castrate (C) does at doses that also inhibited FSH release by cultured rat pituitary cells. Basal FSH release by I cells was inhibited greater than 10% by 0.02% (vol/vol) and greater than 90% by greater than or equal to 0.2% pFFx, whereas in C cells maximal inhibition of FSH release plateaued at only approximately 75%. FSH secretion was restored after removal of pFFx in day 2 media. Luteinizing hormone (LH) release by C cells was not inhibited at any dose of pFFx, but in I cells LH was progressively inhibited to approximately 60% of control levels during day 2 (but not day 1). Charcoal-extracted media (0.25-1%) in which 5 X 10(5) rabbit granulosa cells had been earlier cultured for 72 h produced a parallel inhibition of FSH release. The present findings demonstrate that 1) rabbit pituitary cells are responsive to inhibin, i.e., pFFx preferentially inhibited FSH secretion in a direct, graded, and reversible manner and 2) rabbit follicular granulosa cells secrete an inhibin-like substance.

Induction by Tumor Necrosis Factor-Alpha of Rapid Release of Immunoreactive and Bioactive Luteinizing Hormone from Rat Pituitary Cells in vitro

1990 ◽  
Vol 52 (5) ◽  
pp. 468-472 ◽  
Author(s):  
Masaaki Yamaguchi ◽  
Masahiro Sakata ◽  
Noboru Matsuzaki ◽  
Koji Koike ◽  
Akira Miyake ◽  
...  
Keyword(s):  
Tumor Necrosis Factor ◽  
Tumor Necrosis ◽  
Pituitary Cells ◽  
Necrosis Factor Alpha ◽  
Rapid Release ◽  
Rat Pituitary ◽  
Factor Alpha ◽  
Rat Pituitary Cells ◽  
Necrosis Factor

Progesterone together with estradiol promotes luteinizing hormone β-subunit mRNA stability in rat pituitary cells cultured in vitro

1996 ◽  
Vol 134 (2) ◽  
pp. 236-242 ◽  
Author(s):  
Deokbae Park ◽  
Minseok cheon ◽  
Changmee Kim ◽  
Kyungjin Kim ◽  
Kyungza Ryu
Keyword(s):  
Mrna Stability ◽  
Actinomycin D ◽  
Pituitary Cells ◽  
Mrna Levels ◽  
Ovarian Steroids ◽  
Subunit Mrna ◽  
Rat Pituitary ◽  
Lh Release ◽  
Rat Pituitary Cells

Park D, Cheon M, Kim C, Kim K, Ryu K. Progesterone together with estradiol promotes luteinizing hormoneβ-subunit mRNA stability in rat pituitary cells in vitro. Eur J Endocrinol 1996;134:236–42. ISSN 0804–4643 The present study examined the role of ovarian steroids, estradiol and/or progesterone in the regulation of luteinizing hormone β-subunit (LH-β) mRNA levels and LH release in the rat anterior pituitary cells cultured in vitro. When estradiol (10 nmol/l and/or progesterone (100 nmol/l) were added to the cultures, neither estradiol or progesterone nor both together altered the basal LH-β mRNA levels or LH release. Continuous exposure to gonadotropin-releasing hormone (GnRH, 0.2 nmol/l) for 24 h markedly induced LH-β mRNA accumulation, and in this experimental condition, progesterone alone and progesterone + estradiol further augmented GnRH-induced LH-β mRNA levels and LH release. Then we explored further the possibility that ovarian steroids are involved in modulating LH-β mRNA stability in cultured rat pituitary cells where transcription was inhibited by actinomycin D. Anterior pituitary cells were preincubated with GnRH (0.2 nmol/l) for 16 h and, after removing GnRH from culture medium, the cells were incubated further in the presence of actinomycin D (5 μmol/l) for 24 h. The LH-β mRNA levels gradually declined to about 30% of the control values (zero time point after GnRH removal) in a time-dependent manner. During this period, either progesterone alone or progesterone + estradiol clearly blocked the degradation of LH-β mRNA species. These results indicate that ovarian steroids promote LH-β mRNA stability, thereby contributing to the maintenance of GnRH-stimulated LH-β mRNA levels. Kyungza Ryu, Department of Pharmacology, College of Medicine, Yonsei University, 120-749, Seoul, Korea

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