Oxytocin has a role in gonadotrophin regulation in rats

1990 ◽  
Vol 125 (3) ◽  
pp. 425-432 ◽  
Author(s):  
G. Robinson ◽  
J. J. Evans
Keyword(s):  
Follicular Development ◽  
Pituitary Cells ◽  
Lh Surge ◽  
Rat Pituitary ◽  
Lh Release ◽  
Rat Pituitary Cells ◽  
Dose Dependent ◽  
In Vivo Administration

ABSTRACT We previously demonstrated that oxytocin stimulates LH release from rat pituitary cells in vitro and advances follicular development and ovulation in mice in vivo. This study reports an investigation of rat LH levels following in-vivo administration of oxytocin. Injection of oxytocin (10 mIU/g, i.p.) to rats at 07.00, 08.00 and 09.00 h of pro-oestrus or at 09.00, 10.00 and 11.00 h of pro-oestrus advanced the onset of the LH surge (P<0.005) and attainment of peak concentrations of LH (P<0.02) in peripheral blood. On the other hand, the descending phase of the LH surge and the surge amplitude were not altered by oxytocin. Treatment at 05.00, 06.00 and 07.00 h of pro-oestrus or at 11.00, 12.00 and 13.00 h of pro-oestrus had no effect on the LH profile. A higher oxytocin dose (20 mIU/g) inhibited LH release when treatment was begun at 05.00, 07.00 or 09.00 h of pro-oestrus. A lower dose (5 mIU/g) was ineffective in altering LH concentrations. In addition, injections of oxytocin (10 mIU/g) at oestrus, metoestrus or dioestrus had no effect on the release of LH. Thus the efficacy of oxytocin in altering concentrations of LH was dose dependent and also critically affected by the day of the oestrous cycle and the time of pro-oestrus. Removal of endogenous oxytocin activity by the use of an oxytocin receptor antagonist abolished the pro-oestrous LH surge, indicating that oxytocin is a vital physiological component of the LH-releasing mechanism in rats. The study provides unequivocal evidence that oxytocin induces LH release in vivo, but the manifestation of oxytocin activity is dependent upon conditions of exposure. Journal of Endocrinology (1990) 125, 425–432

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.

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

Effects of tri-iodothyronine, cortisol and transcriptional inhibitors on vitamin D3-enhanced thyrotrophin secretion by rat pituitary cells in vitro

1989 ◽  
Vol 121 (3) ◽  
pp. 451-458 ◽  
Author(s):  
M. C. d'Emden ◽  
J. D. Wark
Keyword(s):  
Primary Cultures ◽  
Relative Increase ◽  
Pituitary Cells ◽  
Dihydroxyvitamin D ◽  
Rat Pituitary ◽  
Tsh Secretion ◽  
Dependent Inhibition ◽  
Rat Pituitary Cells

ABSTRACT The hormone 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) has been shown to selectively enhance agonist-induced TSH release in the rat thyrotroph in vitro. The interaction of 1,25-(OH)2D3 with tri-iodothyronine (T3) and cortisol was studied in primary cultures of dispersed anterior pituitary cells. TRH (1 nmol/l)-induced TSH release over 1 h was enhanced by 70% (P<0·01) following exposure to 10 nmol 1,25-(OH)2D3/l for 24 h. Pretreatment with T3 (1 pmol/l–1 μmol/l) for 24 h caused a dose-dependent inhibition of TRH-induced TSH release. Net TRH-induced TSH release was inhibited by 85% at T3 concentrations of 3 nmol/l or greater. Co-incubation with 1,25-(OH)2D3 resulted in enhanced TRH-induced TSH release at all T3 concentrations tested (P<0·001). The increment of TRH-induced TSH release resulting from 1,25-(OH)2D3 pretreatment was equivalent in the presence or absence of maximal inhibitory T3 concentrations. At 1 nmol T3/1, there was a two- to threefold relative increase in 1,25-(OH)2D3-enhanced TRH-induced TSH release. Incubation with cortisol (100 pmol/l–100 nmol/l) had no effect on basal or TRH-induced TSH release, nor did it alter 1,25-(OH)2D3-enhanced TRH-induced TSH release when added 24 h before, or at the time of addition of 1,25-(OH)2D3. Actinomycin D and α-amanitin abolished 1,25-(OH)2D3-enhanced TSH secretion. These data demonstrate that the action of 1,25-(OH)2D3 in the thyrotroph required new RNA transcription, and was not affected by cortisol. In the presence of T3, the response of the thyrotroph to TRH induced by 1,25-(OH)2D3 was increased. We have shown that 1,25-(OH)2D3 has significant effects on the action of TRH and T3 in vitro. These findings support the proposal that 1,25-(OH)2D3 may modulate TSH secretion in vivo. Journal of Endocrinology (1989) 121, 451–458

Effects of a novel 21-amino steroid, U74006F, on the rat pituitary-adrenocortical axis

1990 ◽  
Vol 126 (2) ◽  
pp. 203-209 ◽  
Author(s):  
J. M. Burrin ◽  
G. R. Hart
Keyword(s):  
Lipid Peroxidation ◽  
Chronic Administration ◽  
Pituitary Cells ◽  
Acth Secretion ◽  
Short Term ◽  
Rat Pituitary ◽  
Rat Pituitary Cells ◽  
Adrenalectomized Rats

ABSTRACT The 21-amino steroid U74006F is a potent inhibitor of lipid peroxidation and has been shown to affect beneficially the acutely injured central nervous system. Therapeutically, it is desirable for this compound to be devoid of steroid side-effects. We have demonstrated a significant (P < 0·001) inhibition of basal ACTH secretion from cultured rat pituitary cells during a 24-h incubation at concentrations (10–100 μmol/l) previously demonstrated to inhibit lipid peroxidation in vitro. U74006F also inhibited corticotrophin-releasing factor (CRF)-stimulated ACTH secretion significantly and the combination of dexamethasone and U74006F completely blocked CRF-41-stimulated ACTH secretion. Administration of U74006F in vivo (30 mg/kg, orally, every 6 h for 30 h) had no effect on ACTH levels in normal rats (84±38 vs 45±6 ng/l in control animals) but increased ACTH levels in adrenalectomized rats (1330±295 vs 464±79 ng/l in control animals, P < 0·02). This increase in ACTH was not observed when adrenalectomized animals were maintained on the same regime of U74006F for 5 days. Our data suggest that U74006F is capable of exerting inhibitory effects on ACTH secretion in vitro. In vivo, effects on ACTH secretion were stimulatory rather than inhibitory and only occurred short-term in adrenalectomized animals or chronically in adrenalectomized rats maintained on dexamethasone. No effects on the pituitary-adrenocortical axis were seen following short-term or chronic administration of U74006F in normal rats. Journal of Endocrinology (1990) 126, 203–209

Burmese Russell's viper venom causes hormone release from rat pituitary cells in vitro

1989 ◽  
Vol 122 (2) ◽  
pp. 489-494 ◽  
Author(s):  
G. R. Hart ◽  
C. Proby ◽  
G. Dedhia ◽  
T. H. Yeo ◽  
G. F. Joplin ◽  
...  
Keyword(s):  
Pituitary Hormone ◽  
Pituitary Cells ◽  
Hormone Release ◽  
Independent Manner ◽  
Column System ◽  
Rat Pituitary ◽  
Russell’S Viper ◽  
Rat Pituitary Cells

ABSTRACT Acute and chronic hypopituitarism is associated with severe envenoming by the Burmese Russell's viper. We have demonstrated that in vitro, Burmese Russell's viper venom (0·1–10 μg/ml) causes a dose-dependent release of GH, TSH and ACTH from dispersed rat anterior pituitary cells in culture. At 10 μg/ml, venom causes a significant increase in the release of GH (344%, P<0·001), TSH (168%, P<0·005) and ACTH (>700%, P<0·001). We have also shown that the component (or components) responsible for this stimulatory effect is stable to heat (60 °C, 1 h) and mild trypsinization. Repeated addition of venom (1 μg/ml) to pituitary cells in a perifusion column system demonstrated attenuation of GH release. This reduced response was not due to depletion of the GH pool since the pituitary cells were subsequently able to respond to both GH-releasing factor (GRF) stimulation and KCl depolarization. Somatostatin in a dose which abolished GRF-stimulated GH release failed to affect venom-stimulated GH release, implying that venom acts in a cyclic AMP-independent manner. We conclude that Burmese Russell's viper venom has direct effects on pituitary hormone release in vitro. Whether these effects contribute to its known actions in vivo on the function of the pituitary remains to be established. Journal of Endocrinology (1989) 122, 489–494

Thymopoietin and thymopentin enhance the levels of ACTH, β-endorphin and β-lipotropin from rat pituitary cells in vitro

1987 ◽  
Vol 115 (4) ◽  
pp. 455-460 ◽  
Author(s):  
M. G. Malaise ◽  
M. T. Hazee-Hagelstein ◽  
A. M. Reuter ◽  
Y. Vrinds-Gevaert ◽  
G. Goldstein ◽  
...  
Keyword(s):  
Cell Model ◽  
Pituitary Cell ◽  
Pituitary Cells ◽  
Clinical Parameters ◽  
Experimental Conditions ◽  
Rat Pituitary ◽  
Dose Dependent Fashion ◽  
Rat Pituitary Cells ◽  
Dose Dependent

Abstract. Thymopoietin and thymopentin are well characterized polypeptides influencing immunoregulation by several mechanisms. Proposed as a therapy in diseases with major immune abnormalities such as rheumatoid arthritis, thymopentin improved within 2 weeks some clinical parameters as pain and joint swelling. The hypothesis that this spectacular effect could be mediated through interactions with anti-inflammatory (ACTH) and pain relieving (β-endorphin) hormones producing cells was tested on the rat isolated pituitary cell model. Thymopentin and thymopoietin can enhance in vitro the levels of ACTH, β-endorphin and β-lipotropin in a time- and dose-dependent fashion for physiological concentrations ranging from 10−12 to 10−8 mol/l. The action on pituitary cells was restricted to those molecules as no changes occurred in LH, FSH, GH, TSH and PRL levels, after otherwise identical experimental conditions.

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.

In-vitro secretion of inhibin-like activity by Sertoli cells from normal and prenatally irradiated immature rats

1986 ◽  
Vol 109 (3) ◽  
pp. 411-418 ◽  
Author(s):  
A. M. Ultee-van Gessel ◽  
F. G. Leemborg ◽  
F. H. de Jong ◽  
H. J. van der Molen
Keyword(s):  
Sertoli Cells ◽  
Culture Media ◽  
Calf Serum ◽  
Pituitary Cells ◽  
Spermatogenic Cells ◽  
Cell Culture Media ◽  
Rat Pituitary ◽  
Rat Pituitary Cells

ABSTRACT The influence of in-vitro conditions on the production of inhibin by Sertoli cells from 21-day-old normal and prenatally irradiated rat testes was studied by measuring inhibin activity in culture media, using the suppression of the release of FSH from cultured rat pituitary cells. Sertoli cells secreted inhibin-like activity during at least 21 days of culture, and cells cultured at 37 °C produced significantly more inhibin than those cultured at 32 °C. The presence of fetal calf serum had no significant effect on inhibin production at 32 °C, while at 37 °C the production was decreased. The presence of ovine FSH stimulated inhibin secretion, while inhibin concentrations in Sertoli cell culture media were decreased after the addition of testosterone. Testosterone, added together with ovine FSH, suppressed inhibin secretion when compared with the levels found in the presence of FSH alone. The presence of spermatogenic cells decreased the release of inhibin. From these results it was concluded that both Sertoli cells isolated from normal immature rat testes and those from testes without spermatogenic cells can secrete inhibin-like activity in culture. A number of discrepancies with in-vivo observations was observed. Therefore, it is likely that the in-vivo situation is too complicated for direct study of the regulation of inhibin production, because of mutual interactions between the testicular compartments. J. Endocr. (1986) 109, 411–418

Sign in / Sign up

Export Citation Format

Share Document