Effect of clomiphene citrate on the in vitro release of LH and FSH by the pituitary gland of the long-term ovariectomized rat pretreated with LRH or with LRH and oestradiol benzoate

1986 ◽  
Vol 113 (1) ◽  
pp. 35-41
Author(s):  
G. A. Schuiling ◽  
H. Moes ◽  
T. R. Koiter
Keyword(s):  
Clomiphene Citrate ◽  
Combined Treatment ◽  
In Vitro Release ◽  
Pituitary Gonadotropin ◽  
Ovx Rats ◽  
Oestradiol Benzoate ◽  
Pituitary Glands ◽  
Pre Treatment

Abstract. The effect of a combined in vivo pre-treatment with luteinizing hormone-releasing hormone (LRH) and either oestradiol benzoate (OB), clomiphene (-citrate) or OB plus clomiphene on the autonomous and the supramaximally LRH-stimulated in vitro secretion of LH and FSH by pituitary glands of long-term ovariectomized (OVX) rats was studied using a hemi-pituitary perifusion system. The concentration of LRH in the perifusion medium was 1 μg/ml. Pre-treatment with LRH during 5 days was effected by means of sc implanted Alzet® osmotic minipumps; control rats received a piece of silastic with the dimensions of a minipump. OB, 3 μg/injection, clomiphene 100 μg/injection or solvent were given on days 2 and 4 (day of perifusion: day 5). In rats not pre-treated with LRH neither OB, nor clomiphene changed the content of the pituitary gonadotropin stores. There was only a small but significant positive effect of the combined treatment with OB and clomiphene on the pituitary FSH content. LRH (partly) depleted the gonadotropin stores. This effect of LRH was potentiated by OB, but not by clomiphene. Clomiphene prevented the depletion-potentiating effect of OB. OB raised the LRH-stimulated secretion of LH and FSH as well as the autonomous secretion of LH. Clomiphene raised the LRH-stimulated (not the autonomous) secretion of LH and FSH. OB plus clomiphene had the same effect as OB alone. Clomiphene also raised the LRH-stimulated secretion of LH and FSH after pre-treatment with LRH, but OB did not do so: LRH prevented the stimulatory effect of OB but not of clomiphene. OB plus clomiphene had the same effect as OB alone. The absence of a stimulatory effect of OB on the LRH-stimulated secretion of LH and FSH in the LRH-pretreated rat appeared to be due to the very low gonadotropin content of the pituitary glands after pre-treatment with LRH and OB: the effect of OB on the LRH-responsiveness proper (i.e. release of LH and FSH as related to the pituitary LH and FSH content) remained stimulatory. Also clomiphene enhanced the LRH-responsiveness proper, but this drug cannot potentiate the gonadotropin stores-depleting effect of LRH. These results demonstrate that clomiphene exclusively 'behaves' like an oestrogen-agonist, able to enhance the LRH-stimulated gonadotropin secretion. Also in the LRH-pre-treated rat clomiphene acts like an oestrogen-agonist, but unlike oestradiol clomiphene cannot potentiate the LRH-induced depletion of the pituitary gonadotropin stores. Therefore, it can also raise the LRH-stimulated secretion of LH and FSH in the LRH-pre-treated OVX rat.

Prolonged combined in vivo pre-treatment with luteinizing hormone-releasing hormone (LRH) and oestradiol benzoate causes long-lasting suppression of the autonomous and the LRH-stimulated secretion of luteinizing hormone and follicle stimulating hormone. An in vitro study

1984 ◽  
Vol 105 (4) ◽  
pp. 468-473 ◽  
Author(s):  
G. A. Schuiling ◽  
H. Moes ◽  
T. R. Koiter
Keyword(s):  
Luteinizing Hormone ◽  
Pituitary Gland ◽  
In Vitro Release ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Oestradiol Benzoate ◽  
Pituitary Glands ◽  
Pre Treatment

Abstract. The effect of a combined in vivo pre-treatment with luteinizing hormone-releasing hormone (LRH) and oestradiol benzoate (EB) on the autonomous and the 'supra-maximally' LRH-stimulated in vitro release of LH and FSH by pituitary glands of 2 weeks ovariectomized (OVX) rats was studied using a perifusion system. The concentration of LRH in the perifusion medium was 1 μg/ml. Pre-treatment with LRH during 6 days was effected by means of sc implanted Alzet® osmotic minipumps (MP). Control rats received a piece of silastic with the dimesions of a minipump ('sham-pump'; Sh-P). EB, 3 μg/injection or solvent (arachis oil) was sc injected on days –3 and –1 (day of perifusion: day 0). Of the pituitary glands of EB-injected, Sh-P-implanted rats both the autonomous and the LRH-stimulated secretion of LH and the LRH-stimulated secretion of FSH were significantly higher than those of the oil-injected, Sh-P-implanted rats without EB administration. Pretreatment with LRH for 6 days had a suppressing effect on the autonomous and the LRH-induced depletion of the pituitary LH and FSH stores. In combination with EB, the suppressing effect of LRH pre-treatment on the LRH-stimulated secretion of LH and FSH was still greater: the pituitary gland appeared to be fixed in a relatively unresponsive state with very low autonomous LH and FSH secretion. It is discussed that increase of pituitary LRH-responsiveness due to EB demands withdrawal of the pituitary gland from the influence of LRH, an effect which is in vivo achieved by the negative feedback of oestrogen on the hypothalamus.

The depressing (negative) effect of oestradiol benzoate on the in vitro secretion of LH and FSH by the pituitary gland of the LRH-pretreated long-term ovariectomized rat changes into the augmentative (positive) effect after discontinuation of the LRH-pretreatment

1985 ◽  
Vol 110 (3) ◽  
pp. 329-337 ◽  
Author(s):  
G. A. Schuiling ◽  
H. Moes ◽  
T. R. Koiter
Keyword(s):  
Depressing Effect ◽  
Ovx Rats ◽  
Gonadotrophin Secretion ◽  
Oestradiol Benzoate ◽  
Negative Effect ◽  
Positive Effect ◽  
Perifusion System

Abstract. The effect of pretreatment in vivo with oestradiol benzoate on in vitro secretion of LH and FSH was studied in long-term ovariectomized (OVX) rats both at the end of a 5-day continuous in vivo pretreatment with LRH and 4-days after cessation of such LRH pretreatment. Rats were on day 0 sc implanted with osmotic minipumps which released LRH at the rate of 250 ng/h. Control rats were implanted with a piece of silicone elastomer with the dimensions of a minipump. On days 2 and 4 the rats were injected with either 3 μg EB or with oil. On day 5 part of the rats were decapitated and the in vitro autonomous (i.e. non-LRH-stimulated) and 'supra-maximally' LRHstimulated release of LH and FSH was studied using a perifusion system. From other rats the minipumps were removed on day 5 and perifusion was performed on day 9. On the 5th day of the in vivo LRH pretreatment the pituitary LH/FSH stores were partially depleted; the pituitaries of the EB-treated rats more so than those of the oil-injected rats. EB alone had no significant effect on the content of the pituitary LH- and FSH stores. On day 9, i.e. 4 days after removal of the minipumps, the pituitary LH and FSH contents had increased in both the oil- and the EB injected rats, but had not yet recovered to control values. In rats not subjected to the 5-days pretreatment with LRH EB had a positive effect on the supra-maximally LRH-stimulated secretion of LH and FSH as well as on the non-stimulated secretion of LH. EB had no effect on the non-stimulated secretion of FSH. After 5 days of in vivo pretreatment with LRH only, the in vitro non-stimulated and supra-maximally LRH-stimulated secretion of both LH and FSH were strongly impaired, the effect correlating well with the LRH-induced depletion of the pituitary LH/FSH stores. In such LRH-pretreated rats EB had on day 5 a negative effect on the (already depressed) LRH-stimulated secretion of LH (not on that of FSH). EB had no effect on the non-stimulated LH/FSH secretion. It could be demonstrated that the negative effect of the combined LRH/EB pretreatment was mainly due to the depressing effect of this treatment on the pituitary LH and FSH stores: the effect of oestradiol on the pituitary LRH-responsiveness (release as related to pituitary gonadotrophin content) remained positive. In LRH-pretreated rats, however, this positive effect of EB was smaller than in rats not pretreated with LRH. Four days after removal of the minipumps there was again a positive effect of EB on the LRH-stimulated secretion of LH and FSH as well as on the non-stimulated secretion of LH. The positive effect of EB on the pituitary LRH-responsiveness was as strong as in rats which had not been exposed to exogenous LRH. The non-stimulated secretion of FSH was again not affected by EB. The results demonstrate that the effect of EB on the oestrogen-sensitive components of gonadotrophin secretion consists of two components: an effect on the pituitary LRH-responsiveness proper, and an effect on the pituitary LH/FSH stores. The magnitude of the effect of EB on the LRH-responsiveness is LRH dependent: it is very weak (almost zero) in LRH-pretreated rats, but strong in rats not exposed to LRH as well as in rats of which the LRH-pretreatment was stopped 4 days previously. Similarly, the effect of EB on the pituitary LH and FSH stores is LRH-dependent: in the absence of LRH, EB has no influence on the contents of these stores, but EB can potentiate the depleting effect of LRH on the LH/FSH-stores. Also this effect disappear after cessation of the LRH-pretreatment.

Release of LH in vitro from anterior pituitary glands of ovariectomized rats by LRH or elevated potassium concentration after pre-treatment with oestradiol benzoate in vivo

1982 ◽  
Vol 99 (2) ◽  
pp. 206-210 ◽  
Author(s):  
A. M. I. Tijssen ◽  
J. de Koning ◽  
G. P. van Rees
Keyword(s):  
Ovariectomized Rats ◽  
Bicarbonate Buffer ◽  
High K ◽  
Oestradiol Benzoate ◽  
Negative Effect ◽  
Pituitary Glands ◽  
Lh Release ◽  
Pre Treatment ◽  
Positive Effect

Abstract. Pituitary glands from ovariectomized rats which had been pre-treated with oestradiol benzoate (OeB) or solvent oil were incubated in Krebs-Ringer bicarbonate buffer with glucose containing either LRH (1000 ng/ml) or a high K+ concentration (50 mM). OeB (7 μg sc) or oil was injected at 2.5 or 6.5 h before the beginning of the incubation experiment or during the three preceding days (three daily injections). Depending upon the period during which the pituitary glands had been exposed to OeB LH release induced by LRH was inhibited (negative effect of OeB) or augmented (positive effect). When the glands were incubated in medium containing high K+, only the negative effect of OeB pre-treatment was seen. It is concluded that that part of LRH-induced LH release which is mimicked by high K+ is involved in the negative effect of OeB, but not in its positive effect.

Effect of pretreatment of long-term ovariectomized (OVX) rats with a competitive LRH antagonist on FSH release in vitro

1985 ◽  
Vol 109 (4) ◽  
pp. 481-484
Author(s):  
J. A. M. J. van Dieten ◽  
G. P. van Rees
Keyword(s):  
Specific Effect ◽  
High Concentration ◽  
Ovx Rats ◽  
High K ◽  
Basal Release ◽  
Pituitary Glands ◽  
Lh Release ◽  
Release In Vitro

Abstract. The effect of a single sc injection of an LRH antagonist ((Ac - D - p - Cl - Phe1,2,D-Trp3,D-Phe6,D-Ala10)-LRH, Org 30093) into OVX rats on FSH release 24 h later was studied. Plasma FSH was decreased but pituitary FSH content was not changed. Incubation of the pituitary glands during 4 h resulted in a decreased basal release. FSH release induced by a low concentration of LRH (1 ng/ml) was depressed but that of a high concentration (10000 ng/ml) was augmented in comparison to FSH release induced in control glands. However, pretreatment with the antagonist had no specific effect on FSH release in vitro induced by high K+ or high K+ plus mbcAMP and theophylline, indicating that the changes of pituitary responsiveness to LRH are not caused by those parts of the secretory mechanism which are stimulated by these secretagogues. Moreover, it is concluded that the changes of pituitary LH release induced by administration of an LRH antagonist also concern FSH.

Effect of pre-treatment of long-term ovariectomized rats with anti-LRH on the response of the pituitary gland in vitro to the analogue of LRH D-ser-(tBu)6-des-gly10-ethylamide-LRH (Buserelin®)

1983 ◽  
Vol 104 (3) ◽  
pp. 272-278 ◽  
Author(s):  
G. P. van Rees ◽  
J. A. M. J. van Dieten ◽  
J. de Koning ◽  
A. F. P. M. de Goey
Keyword(s):  
Pituitary Gland ◽  
Ovariectomized Rats ◽  
Rabbit Serum ◽  
Normal Rabbit Serum ◽  
Basal Release ◽  
Pituitary Glands ◽  
Lh Release ◽  
Pre Treatment

Abstract. Ovariectomized rats were injected iv with an antiserum against LRH or normal rabbit serum. AntiLRH caused a decrease of plasma LH and FSH. After 24 or 48 h, the rats were decapitated and the pituitary glands incubated in the presence of an analogue of LRH which reacts minimally with anti-LRH (Buserelin). Pretreatment with anti-LRH caused an increased response of pituitary LH release to Buserelin. Similar results were obtained with regard to FSH. In this case, however, basal release of FSH was lowered by pre-treatment with antiLRH. Pituitary LH and FSH contents were not affected by anti-LRH, but synthesis of LH and FSH in vitro was smaller than in control glands obtained from rats pretreated with normal rabbit serum.

scholarly journals Long-term maintenance of high rates of very-low-density-lipoprotein secretion in hepatocyte cultures. A model for studying the direct effects of insulin and insulin deficiency in vitro

1989 ◽  
Vol 263 (3) ◽  
pp. 937-943 ◽  
Author(s):  
J M Duerden ◽  
S M Bartlett ◽  
G F Gibbons
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Secretory Process ◽  
Very Low Density Lipoprotein ◽  
Low Density ◽  
Triacylglycerol Synthesis ◽  
Vldl Secretion ◽  
Pre Treatment

High rates of hepatic cellular triacylglycerol synthesis and very-low-density-lipoprotein (VLDL) triacylglycerol output were maintained in vitro for at least 3 days when hepatocytes were cultured in a medium lacking insulin but supplemented with 1 microM-dexamethasone, 10 mM-lactate, 1 mM-pyruvate and 0.75 mM-oleate (supplemented medium). Under these conditions VLDL output remained constant, whereas cell triacyglycerol content increased 10-fold over 3 days, suggesting that the secretory process was saturated. Insulin, present during the first 24 h period, enhanced the storage of cellular triacylglycerol by inhibiting the secretion of VLDL. This stored triacyglycerol was subsequently released into the medium as VLDL if insulin was removed. With the supplemented medium the increased rate of VLDL secretion after insulin removal exceeded that observed under ‘saturating’ conditions, suggesting that pre-treatment with insulin enhanced the capacity for VLDL secretion. In contrast with the short-term (24 h) effects of insulin, longer-term exposure (greater than 48 h) to insulin enhanced the secretion of VLDL compared with insulin-untreated cultures. Under these conditions, insulin increased the net rates of triacylglycerol synthesis. The results suggest that insulin affects the secretion of VLDL triacylglycerol by two distinct and opposing mechanisms: first, by direct inhibition of secretion; second by increasing triacylglycerol synthesis, which stimulates secretion. The net effect at any time depends upon the relative importance of each of these processes.

Long-term effects of a gonadotrophin-releasing hormone agonist ([d-Ser(But)6]GnRH(1–9)nonapeptide-ethylamide) on gonadotrophin secretion from human pituitary gonadotroph cell adenomas in vitro

1988 ◽  
Vol 118 (3) ◽  
pp. 491-496 ◽  
Author(s):  
M. Daniels ◽  
P. Newland ◽  
J. Dunn ◽  
P. Kendall-Taylor ◽  
M. C. White
Keyword(s):  
Gnrh Agonist ◽  
In Vitro Release ◽  
Long Term Effects ◽  
Human Pituitary ◽  
Α Subunit ◽  
Releasing Hormone ◽  
Gonadotrophin Secretion ◽  
Gonadotrophin Releasing Hormone

ABSTRACT We have studied the effects of TRH and native gonadotrophin-releasing hormone (GnRH), and of a GnRH agonist (Buserelin; [d-Ser(But)6]GnRH(1–9) nonapeptide-ethylamide), on LH, FSH, α subunit and LH-β subunit secretion from three human gonadotrophin-secreting pituitary adenomas in dispersed cell culture. During a 24 h study, treatment with 276 nmol TRH/1 resulted in a significant (P < 0·05) stimulated release of FSH and α subunit from all three adenomas, and LH from the two adenomas secreting detectable concentrations of this glycoprotein; treatment with 85 nmol GnRH/l significantly (P < 0·05) stimulated the release of α subunit from all three, but FSH from only two and LH from only one adenoma. During a long-term 28-day study, basal FSH and α subunit concentrations were maintained, but secretion of LH, and LH-β (detectable from one tumour only), declined with time from two of the three adenomas. Addition of Buserelin to the cultures resulted in the continuous (P < 0·05) stimulation of α subunit secretion from all three adenomas, and of LH and FSH from two, whilst a transient stimulatory effect on LH and FSH secretion was seen from a third adenoma, with subsequent secretion rates declining towards control values. These data show that human gonadotrophin-secreting adenomas demonstrate variable stimulatory responses to hypothalamic TRH and GnRH, and that during chronic treatment with a GnRH agonist the anticipated desensitizing effect of the drug was not observed in two out of three adenomas studied. The mechanism for this is not clear, but such drugs are unlikely to be of therapeutic value in the management of gonadotrophin-secreting tumours. The data also suggest that GnRH and GnRH agonists have a differential effect on the in-vitro release of intact gonadotrophins and the common α subunit. J. Endocr. (1988) 118, 491–496

scholarly journals Inhibition of salmon calcitonin on secretion of progesterone and GnRH-stimulated pituitary luteinizing hormone

1999 ◽  
Vol 277 (1) ◽  
pp. E49-E55 ◽  
Author(s):  
Shiow-Chwen Tsai ◽  
Chien-Chen Lu ◽  
Jiann-Jong Chen ◽  
Yu-Chung Chiao ◽  
Shyi-Wu Wang ◽  
...  
Keyword(s):  
Luteinizing Hormone ◽  
Granulosa Cells ◽  
Salmon Calcitonin ◽  
Inhibitory Effect ◽  
Female Rats ◽  
Progesterone Production ◽  
Ovx Rats ◽  
Pituitary Glands

The effects of salmon calcitonin (sCT) on the production of progesterone and secretion of luteinizing hormone (LH) were examined in female rats. Diestrous rats were intravenously injected with saline, sCT, human chorionic gonadotropin (hCG), or hCG plus sCT. Ovariectomized (Ovx) rats were injected with saline or sCT. In the in vitro experiments, granulosa cells and anterior pituitary glands (APs) were incubated with the tested drugs. Plasma LH levels of Ovx rats were reduced by sCT injection. Administration of sCT decreased the basal and hCG-stimulated progesterone release in vivo and in vitro. 8-Bromo-cAMP dose dependently increased progesterone production but did not alter the inhibitory effect of sCT. H-89 did not potentiate the inhibitory effect of sCT. Higher doses of 25-hydroxycholesterol and pregnenolone stimulated progesterone production and diminished the inhibitory effects of sCT. sCT did not decrease basal release of LH by APs, but pretreatment of sCT decreased gonadotropin-releasing hormone (GnRH)-stimulated LH secretion. These results suggested that sCT inhibits progesterone production in rats by preventing the stimulatory effect of GnRH on LH release in rat APs and acting directly on ovarian granulosa cells to decrease the activities of post-cAMP pathway and steroidogenic enzymes.

PROGESTERONE TREATMENT INCREASES PITUITARY OESTRADIOL RETENTION IN THE OVARIECTOMIZED NORMAL FEMALE RAT BUT NOT IN THE MALE NOR IN THE ANDROGEN- OR OESTROGEN-STERILIZED FEMALE RAT

1977 ◽  
Vol 84 (2) ◽  
pp. 268-280 ◽  
Author(s):  
Robert D. Lisk ◽  
Lawrence A. Reuter
Keyword(s):  
Testosterone Propionate ◽  
Ovariectomized Rats ◽  
Normal Female ◽  
Nuclear Fraction ◽  
Female Rat ◽  
Treatment Conditions ◽  
Oestradiol Benzoate ◽  
Pre Treatment

ABSTRACT Pituitary retention of [3H]oestradiol in ovariectomized rats was measured following in vivo progesterone pre-treatment and found to be significantly increased after 48, 72, 96 and 120 h of pre-treatment. Increased [3H]oestradiol retention was also observed for at least up to 72 h after removal of the progesterone pre-treatment source. This retention was measured as dpm per mg dry tissue weight. [3H]Oestradiol retention was also measured in the nuclear fraction of tissues incubated with [3H]oestradiol in vitro. Following 72 h of in vivo progesterone pre-treatment, the nuclear fraction from the pituitary was found to retain significantly more [3H]oestradiol than corresponding fractions from non-treated animals. In contrast to ovariectomized females, no increase in [3H]oestradiol retention was found in the pituitary of orchidectomized males pre-treated with progesterone for 72 h. [3H]Oestradiol retention by pituitaries of ovariectomized rats injected on the day of birth with 200 μg oestradiol benzoate (OeB) or 500 μg testosterone propionate (TP) was significantly decreased in comparison to control animals. When the rats were pre-treated in vivo with oestradiol for 6 or 72 h and [3H]oestradiol retention was measured 6 or 24 h after this pre-treatment, the OeB and TP treated animals retained significantly less [3H]oestradiol under most treatment conditions. Progesterone pretreatment for 24 or 72 h in vivo followed by measurement of [3H]oestradiol retention immediately or 6 or 24 h later resulted in a significant increase in [3H]oestradiol retention for the control animals. In contrast, the neonatally OeB or TP treated animals differed significantly by not showing increased retention. When [3H]oestradiol retention of the pituitary was measured in vitro following homogenization at 0°C and incubation at 37°C for 1 h, the nuclear fraction from both OeB and TP treated animals was found to retain less hormone per unit DNA; however, this decrease was significant only for the TP animals. Thus, males and androgen- or oestrogensterilized females have an altered and reduced augmentation of pituitary oestradiol retention in response to both oestrogen and progesterone pretreatments.

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