EFFECTS OF CLOMIPHENE ON THE PHYSIOLOGY OF REPRODUCTION IN THE RAT

ABSTRACT The uptake of intravenously administered tritiated oestradiol by the uterus and pituitary gland of untreated, as well as clomiphene pretreated immature rats was studied to elucidate the nature of the antioestrogenic action of clomiphene. The results indicate that this agent competes with the natural oestrogen for the receptor sites in the uterus and pituitary gland and prevents the entry of oestrogen to and probably displaces it from the receptor sites. The significance of these observations with respect to the ability of clomiphene for the induction of ovulation in anovulatory women is discussed.

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The induction of ovulation in the rabbit, by electrical stimulation of the hypothalamo-hypophysial mechanism

Proceedings of the Royal Society of London Series B Biological Sciences ◽

10.1098/rspb.1937.0031 ◽

1937 ◽

Vol 122 (828) ◽

pp. 374-394 ◽

Cited By ~ 82

Keyword(s):

Electrical Stimulation ◽

Pituitary Gland ◽

Anterior Lobe ◽

Present Position ◽

Nervous Stimulation ◽

Gonadotropic Hormone ◽

Genital Region ◽

Induction Of Ovulation ◽

Hormonal Factor ◽

Stimulation Of

In two recent papers, by Marshall and Verney (1936), and by Harris (1936), the mechanism concerned with ovulation in the rabbit has been fully discussed. In view of this, only a brief summary of the present position will be given here. Ovulation in the rabbit occurs normally only after some form of sexual excitement. There is much evidence to show that the factors involved are: first, a nervous stimulation from the genital region and perhaps from the cortex, acting on the anterior lobe of the pituitary gland; and secondly, a hormonal factor, the pituitary gland secreting a gonadotropic hormone which affects the ovaries.

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Nitric oxide sensitive-guanylyl cyclase subunit expression changes during estrous cycle in anterior pituitary glands

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.90795.2008 ◽

2009 ◽

Vol 296 (4) ◽

pp. E731-E737 ◽

Cited By ~ 13

Author(s):

Jimena P. Cabilla ◽

Sonia A. Ronchetti ◽

Silvana I. Nudler ◽

Eliana A. Miler ◽

Fernanda A. Quinteros ◽

...

Keyword(s):

Nitric Oxide ◽

Pituitary Gland ◽

Estrous Cycle ◽

Guanylyl Cyclase ◽

Anterior Pituitary ◽

Acute Treatment ◽

Α Subunit ◽

Immature Rats ◽

Subunit Expression ◽

Pituitary Glands

17β-Estradiol (E2) exerts inhibitory actions on the nitric oxide pathway in rat adult pituitary glands. Previously, we reported that in vivo E2 acute treatment had opposite effects on soluble guanylyl cyclase (sGC) subunits, increasing α1- and decreasing β1-subunit protein and mRNA expression and decreasing sGC activity in immature rats. Here we studied the E2 effect on sGC protein and mRNA expression in anterior pituitary gland from adult female rats to address whether the maturation of the hypothalamus-pituitary axis influences its effects and to corroborate whether these effects occur in physiological conditions such as during estrous cycle. E2 administration causes the same effect on sGC as seen in immature rats, and these effects are estrogen receptor dependent. These results suggest that E2 is the main effector of these changes. Since the sGC α-subunit increases while the sGC activity decreases, we studied if other less active isoforms of the sGC α-subunit are expressed. Here we show for the first time that sGCα2 and sGCα2 inhibitory (α2i) isoforms are expressed in this gland, but only sGCα2i mRNA increased after E2 acute treatment. Finally, to test whether E2 effects take place under a physiological condition, sGC subunit expression was monitored over estrous cycle. sGCα1, -β1, and -α2i fluctuate along estrous cycle, and these changes are directly related with E2 level fluctuations rather than to NO level variations. These findings show that E2 physiologically regulates sGC expression and highlight a novel mechanism by which E2 downregulates sGC activity in rat anterior pituitary gland.

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Induced breeding of the riverine catfish Rita rita

Journal of the Bangladesh Agricultural University ◽

10.3329/jbau.v6i2.4835 ◽

1970 ◽

Vol 6 (2) ◽

pp. 361-366

Author(s):

MFA Molla ◽

MR Amin ◽

MN Sarowar ◽

M Muhammadullah

Keyword(s):

Body Weight ◽

Pituitary Gland ◽

Fertilization Rate ◽

Hatching Rate ◽

Induction Of Ovulation ◽

Successful Induction ◽

Hatching Rates

The paper reports the first incidence of successful induction of breeding in the riverine catfish Rita rita using carp pituitary gland (PG) extract. A breeding trial using four PG doses viz. 80, 100, 120 and 140mg/kg body weight of fish was conducted to optimize the dose of pituitary gland (PG) extract in terms of induction of ovulation in female. The male received a dose of 40mg PG/kg body weight in all cases and was sacrificed for collection of milt. The best performance was shown by the fish treated with 100mg PG/kg body weight in respect of inducing ovulation in females and fertilization and hatching rates of eggs. Keywords: Induced breeding; Rita rita; Ovulation; Fertilization rate; Hatching rate DOI: 10.3329/jbau.v6i2.4835 J. Bangladesh Agril. Univ. 6(2): 361-366, 2008

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Unfilled nuclear oestrogen receptors in the rat brain and pituitary gland

Journal of Endocrinology ◽

10.1677/joe.0.0930327 ◽

1982 ◽

Vol 93 (3) ◽

pp. 327-338 ◽

Cited By ~ 14

Author(s):

C. R. Clark ◽

N. J. MacLusky ◽

F. Naftolin

Keyword(s):

Pituitary Gland ◽

Nuclear Receptor ◽

Dissociation Constants ◽

Ovariectomized Rats ◽

Oestrogen Receptors ◽

Ligand Specificity ◽

Cell Nuclei ◽

Receptor Sites ◽

Equilibrium Dissociation Constants ◽

Equilibrium Dissociation

This study describes the presence of a population of oestrogen receptors in cell nuclei from the pituitary gland and brain of untreated and oestradiol-treated ovariectomized rats. The receptors behaved as if they were not occupied by oestradiol. These 'unfilled' oestrogen receptors could be distinguished from occupied nuclear receptor sites on the basis of their ability to bind [3H]oestradiol at low temperatures (0–4 °C). Occupied receptors bound labelled [3H]oestradiol only under exchange conditions at an increased temperature (25 °C). Unfilled and occupied nuclear receptors were physicochemically similar in terms of sedimentation coefficients in sucrose density gradients containing 0·4 m-KC1 (4–5S), equilibrium dissociation constants for reaction with [3H]oestradiol (0·2–0·6 nmol/l) and ligand specificity. In ovariectomized rats, unfilled receptors constituted more than 75 % of the total nuclear receptor population. One hour after i.v. treatment with oestradiol (3·6 μg/kg), both total and unfilled nuclear receptor concentrations increased and then subsequently declined over the next 12 h. The increase in unfilled sites was, however, proportionately less than that occurring in the filled component; at 1 h after oestradiol injection unfilled sites constituted less than 20% of the receptors present in brain and pituitary cell nuclei. The physiological significance of unfilled nuclear oestrogen receptors remains unknown. The observations that they exist in various oestrogen target tissues and that their levels are influenced by oestradiol treatment suggest a possible role for these receptors in the mechanism of oestrogen action.

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CHANGES IN PITUITARY FSH AND LH AND PLASMA LH IN IMMATURE RATS TREATED WITH PREGNANT MARE'S SERUM

Acta Endocrinologica ◽

10.1530/acta.0.0700220 ◽

1972 ◽

Vol 70 (2) ◽

pp. 220-230

Author(s):

Shao-Yao Ying ◽

Roland K. Meyer

Keyword(s):

Pituitary Gland ◽

Gradual Decrease ◽

Immature Rats

ABSTRACT The concentrations of LH and FSH in the pituitary gland and LH in the plasma from immature rats treated with saline, 3 IU, or 12 IU PMS were measured for 4 days. There was no detectable LH in 1.5 ml of plasma at any time in saline-treated rats. In 3 IU PMS rats, an elevation was observed at 3.00 p. m. and 8.00 p. m. on day 24. The plasma LH level of 12 IU PHS rats was much higher than that of 3 IU PMS rats, reaching a maximum at 10.00 a. m. on day 23, then gradually decreasing until the morning of day 25. The pituitary FSH content in 3 IU PMS rats reached a maximum at 10.00 a. m. on day 24, then drastically decreased at 3.00 p. m. and 8.00 p. m. The pituitary FSH content of 12 IU PMS rats showed a gradual decrease without an acute release on the afternoon of day 24. These results indicate that FSH, like LH, is released on the afternoon of day 24 and may be involved in ovulation. The failure of 12 IU PMS rats to ovulate is probably due to (a) interference in the timing of ovulating hormone (OH) release, (b) lack of a surge of LH, or (c) improper ratio of LH to FSH.

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INDUCTION OF OVULATION BY PREGN-5-ENE-3,20-DIONE AND PROGESTERONE IN IMMATURE RATS TREATED WITH PMSG AND PHENOBARBITAL

Reproduction ◽

10.1530/jrf.0.0390259 ◽

1974 ◽

Vol 39 (2) ◽

pp. 259-266 ◽

Cited By ~ 2

Author(s):

B. N. SRIDHARAN ◽

R. K. MEYER ◽

H. J. KARAVOLAS

Keyword(s):

Induction Of Ovulation ◽

Immature Rats

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Hormonal augmentation of fertility in sheep: I. Induction of ovulation, superovulation and heat in sheep

The Journal of Agricultural Science ◽

10.1017/s0021859600048097 ◽

1942 ◽

Vol 32 (3) ◽

pp. 308-323 ◽

Cited By ~ 28

Author(s):

J. Hammond ◽

A. S. Parkes

Keyword(s):

Pituitary Gland ◽

Pregnant Women ◽

Corpus Luteum ◽

Sexual Receptivity ◽

Pituitary Extract ◽

Normal Range ◽

Induction Of Ovulation

1. Gonadotrophic extracts of horse-pituitary gland, of pregnant mare serum and of urine of pregnant women, as well as oestrogenic substances, will induce ovulation in anoestrous sheep. The number of ova shed is apparently independent of the dosage given and lies within the normal range.2. The oestrogens probably act by evoking ovulation-producing activity on the part of the animal's own pituitary gland, and it is likely that the gonadotrophins also initiate the same chain of events by causing oestrogen secretion by the ovary.3. Oestrogens induce heat in the anoestrous sheep, but horse-pituitary extract and P.M.S. evoked sexual receptivity only in animals having a regressing corpus luteum. In the absence of a corpus luteum, ovulation occurs without heat, while the presence of an active corpus luteum usually suppresses both ovulation and heat.4. Administration of horse pituitary a few days before the corpus luteum is due to regress results in superovulation at the succeeding heat, as many as twelve simultaneous ovulations having been obtained under these conditions.

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EFFECTS OF CLOMIPHENE ON THE PHYSIOLOGY OF REPRODUCTION IN THE RAT

Acta Endocrinologica ◽

10.1530/acta.0.0470657 ◽

1964 ◽

Vol 47 (4) ◽

pp. 657-668 ◽

Cited By ~ 30

Author(s):

Somnath Roy ◽

Robert B. Greenblatt ◽

Virendra B. Mahesh

Keyword(s):

Mode Of Action ◽

Induction Of Ovulation ◽

Receptor Sites

ABSTRACT The oestrogenic and antioestrogenic actions of clomiphene were studied in rats. In the absence of oestrogen in ovariectomized animals it exerted a uterotrophic effect, whereas, in the presence of a natural oestrogen (oestradiol) this compound at the same dosage levels counteracted the uterotrophic effect of the oestrogen. In suitable doses clomiphene also counteracted the gonadotrophin suppressing and ovulation-inhibiting actions of oestradiol. The results suggest that this agent may act by competing with the natural oestrogen for the receptor sites. The possible significance of these observations to the mode of action of clomiphene in the induction of ovulation in anovulatory women is discussed.

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