ANTIGONADOTROPHIC EFFECT OF PROLACTIN IN ADULT CASTRATED AND IN IMMATURE FEMALE RATS

1977 ◽  
Vol 84 (1) ◽  
pp. 62-71 ◽  
Author(s):  
W. Beck ◽  
S. Engelbart ◽  
M. Gelato ◽  
W. Wuttke
Keyword(s):  
High Serum ◽  
Female Rats ◽  
Serum Prolactin ◽  
Intact Female ◽  
Immature Female ◽  
Blood Samples ◽  
Serum Lh ◽  
Male Donor ◽  
Lh Release ◽  
Timing Of Puberty

ABSTRACT High serum prolactin levels were induced in chronically castrated female rats by pituitary transplants from male donor rats. The typical pulsatile LH release pattern observed in castrated control rats was maintained in pituitary grafted rats, when pituitary transplantation was performed simultaneously with castration 3 months before withdrawal of the blood samples. If pituitaries were transplanted into chronically castrated rats and blood samples were withdrawn 3 days later, the pulsatile LH release was abolished and basal or moderately elevated LH levels were found. Chronically or subacutely elevated prolactin levels had no effect on high serum FSH values. Pituitary transplants into intact female rats at day 23 after birth also suppressed basal LH values for 4 days without alterating the serum FSH levels. Six and 8 days after transplantation the serum LH levels were normal. Pituitary transplantation into these immature rats advanced puberty by more than one week. These results indicate that prolactin has an antigonadotrophic effect in female rats which is directed only towards pituitary LH but not FSH secretion. The inhibitory action of high serum prolactin levels on pituitary LH release does not last longer than 4–6 days under steady state conditions, such as found in the constantly high prolactin levels due to pituitary transplants. Under natural conditions with steadily increasing prolactin levels between day 20 and puberty the effect of prolactin in inhibiting pituitary LH release may last longer. Thus, prolactin may be one of the, if not the regulator of the timing of puberty.

EFFECTS OF NALOXONE ON LUTEINIZING HORMONE AND PROLACTIN IN SERUM OF RATS

1980 ◽  
Vol 85 (2) ◽  
pp. 307-315 ◽  
Author(s):  
M. S. BLANK ◽  
A. E. PANERAI ◽  
H. G. FRIESEN
Keyword(s):  
Female Rats ◽  
Male Rats ◽  
Ovariectomized Rats ◽  
Serum Prolactin ◽  
Immature Female ◽  
Subcutaneous Injections ◽  
Serum Lh ◽  
Opiate Peptides ◽  
Lh Release ◽  
Lh Secretion

The effects of subcutaneous injections of the opiate antagonist naloxone on the tonic and phasic secretion of prolactin and LH were studied in rats. During development, resting levels of prolactin in serum were decreased by naloxone (2·5 mg/kg body wt) on days 24,45 and 50 in female rats and on days 28,45 and 50 in male rats. In the adult, naloxone (2·5 mg/kg body wt) decreased basal levels of serum prolactin in male rats and levels during oestrus in female rats. In 25-day-old female rats, serum LH rose from resting levels within 7·5 min of naloxone administration (2·5 mg/kg body wt) and returned to pretreatment levels by 30 min, while prolactin fell by 7·5 min and remained low for as long as 60 min after treatment. Furthermore, a tenfold lower dose of naloxone (0·25 mg/kg body wt) did not raise basal levels of serum LH but still decreased resting levels of serum prolactin in immature female rats (24 days old). The effect of naloxone (2·5 mg/kg body wt) on phasic LH release was studied in 29-day-old immature female rats primed on day 27 with pregnant mare serum gonadotrophin (PMSG). In these PMSG-treated rats the onset of the prolactin surge was blunted by naloxone while it had no effect on phasic LH release. Naloxone (5 mg/kg body wt) also induced a rise in levels of serum LH in ovariectomized rats and, if administered with morphine, it reversed the short-term inhibition of LH secretion caused by morphine. However, naloxone was ineffective after pretreatment with oestradiol benzoate. These findings suggest that the responses of serum LH and prolactin to naloxone were dissociated and that oestrogens and opiate peptides may have interacted to regulate secretion of LH.

SERUM GONADOTROPHIN LEVELS DURING DEVELOPMENT IN MALE, FEMALE AND ANDROGENIZED FEMALE RATS AND THE EFFECT OF GENERAL DISTURBANCE ON HIGH LUTEINIZING HORMONE LEVELS

1976 ◽  
Vol 70 (3) ◽  
pp. 361-371 ◽  
Author(s):  
P. C. B. MACKINNON ◽  
J. M. MATTOCK ◽  
M. B. TER HARR
Keyword(s):  
Wistar Rats ◽  
High Serum ◽  
Female Rats ◽  
Serum Prolactin ◽  
Adult Males ◽  
Serum Lh ◽  
Male Wistar Rats ◽  
Serial Blood Sampling ◽  
Lh Release ◽  
Very High

SUMMARY Serum LH, FSH and prolactin levels were measured in blood samples which were obtained by decapitation from groups of female, neonatally androgenized female and male Wistar rats at 2-day intervals from birth to maturity. An increase in serum FSH levels was observed between 4 and 24 days of age in both the female and androgenized female groups, while a much later increase, between 28 and 44 days of age, occurred in the males. Serum prolactin levels increased gradually from birth in all three groups until adult levels were attained. In contrast, serum LH levels were in general low in all three groups of animals, although very high levels (> 7 ng/ml) were recorded in 22 out of 168 females and 8 out of 192 males between 4 and 28 days of age, as well as in adult males; occasional high LH levels were also seen in the androgenized females. The nature of the high serum LH levels was investigated in anaesthetized and unanaesthetized immature females by serial blood sampling using a number of techniques. Unexpectedly, only three out of 58 animals had high LH levels: two of these showed an episodic form of LH release during which levels increased to peak values and then declined within a period of about 30 min. On investigation it was found that general disturbance within the 45 min before decapitation could inhibit high LH levels in females aged between 23 and 30 days.

SERUM LUTEINIZING HORMONE AND FOLLICLE-STIMULATING HORMONE CONCENTRATIONS IN IMMATURE FEMALE RATS TREATED WITH MULTIPLE INJECTIONS AND VARIOUS AMOUNTS OF LUTEINIZING HORMONE RELEASING HORMONE

1975 ◽  
Vol 66 (1) ◽  
pp. 13-20 ◽  
Author(s):  
D. C. JOHNSON ◽  
R. S. MALLAMPATI
Keyword(s):  
Luteinizing Hormone ◽  
Constant Stimulus ◽  
Female Rats ◽  
Intact Female ◽  
Immature Female ◽  
Luteinizing Hormone Releasing Hormone ◽  
Releasing Hormone ◽  
Serum Luteinizing Hormone ◽  
Serum Lh ◽  
Lh Rh

SUMMARY Release of immunoreactive LH and FSH was induced in immature intact female rats by repeated injections of synthetic luteinizing hormone releasing hormone (LH-RH). Altering the dose of LH-RH (5, 10, 20, 50 ng) and the frequency of administration (every 10, 20, 30 or 60 min) over a period of 2 h produced a variety of serum LH and FSH concentrations and ratios. When the dose was a constant 20 ng but the frequency of injections was either 20 or 30 min, a steady state in serum gonadotrophin concentrations was reached within 1 h and the level remained the same during the second hour. When given every 10 min, 20 ng LH-RH produced a much higher concentration of both LH and FSH during the second hour of stimulation. Examination of the gonadotrophin levels after each injection of LH-RH showed that the pituitary response was variable in spite of a constant stimulus.

Hormone concentrations and ovulatory response in rats treated with antiprogestagens

1991 ◽  
Vol 129 (3) ◽  
pp. 423-429 ◽  
Author(s):  
J. Th. J. Uilenbroek
Keyword(s):  
Cumulus Cells ◽  
High Serum ◽  
Chorionic Gonadotrophin ◽  
Human Chorionic Gonadotrophin ◽  
Ovulation Rate ◽  
Female Rats ◽  
Serum Prolactin ◽  
Lh Surge ◽  
Serum Lh ◽  
Preovulatory Follicles

ABSTRACT Administration of antiprogestagens (2 mg/day) to female rats for 21 days induces high serum prolactin levels. These levels stimulate luteal progesterone production and an increase in ovarian weight. Compared with RU486 (mifepristone) the increase in prolactin is less after treatment with ZK299 (onapristone), an antiprogestagen with lower antiglucocorticoid activity. To study whether cyclic ovulations occur in rats treated with antiprogestagens, 5-day cyclic rats were given daily injections of RU486 or ZK299 (2 mg) from metoestrus (day 1) to pro-oestrus. This treatment advanced the forthcoming ovulation by 1 day; however, the ovulation rate was low. Injection of 10 IU human chorionic gonadotrophin on the afternoon of pro-oestrus (day 3) increased the ovulation rate, but not to the level found in oil-treated rats. Serum LH concentrations measured from metoestrus to oestrus at 10.00 and 17.00 h were higher in antiprogestagen- than in oil-treated rats from day 2 (17.00 h) onwards. A low preovulatory LH surge was found in antiprogestagen-treated rats on the after-noon of pro-oestrus (day 3). Ovarian histology at the day of oestrus (day 4) confirmed the presence of a low LH surge as, besides ruptured follicles, unruptured follicles with dispersion of cumulus cells were present. The pro-oestrous surge of prolactin was also advanced by 24 h. The magnitude, however, was not different from that in oil-treated rats at day 4. In conclusion, daily administration of antiprogestagens to 5-day cyclic rats results in increased basal levels of serum LH and advancement of the preovulatory surge of prolactin and LH by 1 day. The ovulatory response is low due to the low pre-ovulatory surge of LH and to a reduced ability of preovulatory follicles to respond to LH. Journal of Endocrinology (1991) 129, 423–429

OESTROGENS AND PROLACTIN AS POSSIBLE REGULATORS OF PUBERTY

1976 ◽  
Vol 68 (3) ◽  
pp. 391-396 ◽  
Author(s):  
W. WUTTKE ◽  
K. D. DÖHLER ◽  
M. GELATO
Keyword(s):  
Positive Feedback ◽  
High Serum ◽  
Female Rats ◽  
Serum Prolactin ◽  
Early Puberty ◽  
Control Female ◽  
Highly Sensitive ◽  
Specific Antisera ◽  
Lh Release ◽  
Ovine Prolactin

SUMMARY At day 15 after birth, high serum oestradiol levels, high FSH levels and occasionally high LH levels were observed in control female rats. Injections of potent and specific antisera for oestrogen between days 8–15 prevented LH peaks and decreased basal LH levels. Serum FSH levels were increased after treatment. High oestradiol levels at this time appear to exert a positive feedback action on phasic as well as tonic LH release. Injections of ovine prolactin (0·5 μg/g body wt twice daily) between days 8–25 of life significantly advanced the day of vaginal opening in immature rats and initiated regular oestrous cycles. Such treatment completely prevented high LH levels at day 15 but serum FSH levels remained high. Prolactin and progesterone levels were higher at day 25 than at day 15 in control rats and at that time LH and FSH levels were low. Prolactin treatment had a depressant effect on endogenous prolactin and progesterone levels. It is proposed that after day 20 the positive feedback threshold of oestradiol on LH release is at a mature, highly sensitive level. The steady increment in serum prolactin and/or progesterone levels between day 20 and puberty, however, inhibited phasic LH release thus preventing early puberty. The possible mechanisms of action of prolactin are discussed.

Changes in the characteristics of pulsatile luteinizing hormone secretion during the oestrous cycle and after ovariectomy and oestrogen treatment in female rats

1982 ◽  
Vol 94 (2) ◽  
pp. 177-182 ◽  
Author(s):  
Takashi Higuchi ◽  
Masazumi Kawakami
Keyword(s):  
Hormone Secretion ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Oestrous Cycle ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Luteinizing Hormone Secretion ◽  
Oestrogen Treatment ◽  
Serum Lh ◽  
Lh Release

Changes in the characteristics of LH secretory pulses in female rats were determined in different hormonal conditions; during the oestrous cycle and after ovariectomy and oestrogen treatment. The frequency and amplitude of the LH pulses were stable during the oestrous cycle except at oestrus when a pattern could not be discerned because of low LH concentrations. These were significantly lower than those measured during other stages of the cycle. Mean LH concentrations and LH pulse amplitudes increased with time up to 30 days after ovariectomy. The frequency of the LH pulse was unchanged 4 days after ovariectomy when mean LH levels had already increased. The frequency increased 10 days after ovariectomy and then remained stable in spite of a further increase in mean serum LH concentrations. Oestradiol-17β injected into ovariectomized rats caused a decrease in LH pulse amplitude but no change in pulse frequency. One day after treatment with oestradiol benzoate no LH pulse was detectable, probably because the amplitude was too small. A generator of pulsatile LH release is postulated and an oestrogen effect on its function is discussed.

RESTORATION OF OESTROGEN POSITIVE FEEDBACK EFFECT ON LH RELEASE BY BROMOCRIPTINE IN HYPERPROLACTINAEMIC PATIENTS WITH GALACTORRHOEA-AMENORRHOEA

1979 ◽  
Vol 91 (3) ◽  
pp. 591-600 ◽  
Author(s):  
Toshihiro Aono ◽  
Akira Miyake ◽  
Takenori Shioji Motoi Yasuda ◽  
Koji Koike ◽  
Keiichi Kurachi
Keyword(s):  
Luteinizing Hormone ◽  
Follicle Stimulating Hormone ◽  
Serum Prolactin ◽  
Serum Luteinizing Hormone ◽  
Serum Lh ◽  
Lh Release ◽  
The Mean ◽  
Lh Rh ◽  
Lh Releasing Hormone ◽  
Positive Feedback Effect

ABSTRACT Five mg of bromocriptine was administered for 3 weeks to 8 hyperprolactinaemic women with galactorrhoea-amernorrhoea, in whom the response of serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) to 100 μg of iv LH-releasing hormone (LH-RH) had been evaluated. Twenty mg of conjugated oestrogen (Premarin®) was injected iv any day between the 10th and 12th day from the initiation of the treatment, and serum LH levels were serially determined for 120 h. Hyperresponse of LH with normal FSH response to LH-RH was observed in most patients. Bromocriptine treatment for 10 to 12 days significantly suppressed mean (± se) serum prolactin (PRL) levels from 65.1 ± 23.0 to 10.4 ± 2.0 ng/ml, while LH (12.6 ± 2.1 to 24.8 ± 5.9 mIU/ml) and oestradiol (40.1 ± 7.6 to 111.4 ± 20.8 pg/ml) levels increased significantly. Patients on bromocriptine treatment showed LH release with a peak at 48 h after the injection of Premarin. The mean per cent increases in LH were significantly higher than those in untreated patients with galactorrhoea-amenorrhoea between 32 and 96 h after the injection. The present results seem to suggest that the restoration of LH-releasing response to oestrogen following suppression of PRL by bromocriptine may play an important role in induction of ovulation in hyperprolactinaemic patients with galactorrhoea-amenorrhoea.

Effects of acute administration of 2-hydroxylated metabolites of oestrogens on LH and prolactin secretion in male and female prepubertal rats

1984 ◽  
Vol 103 (3) ◽  
pp. 317-325
Author(s):  
A. K. Brar ◽  
G. Fink
Keyword(s):  
Plasma Concentration ◽  
Female Rats ◽  
Male Rats ◽  
Male Rat ◽  
Female Rat ◽  
Uterine Weight ◽  
Immature Female ◽  
Male And Female ◽  
Immature Male ◽  
Lh Release

ABSTRACT The effects of catechol oestradiol and catechol oestrone on the release of LH and prolactin were investigated in immature male and female Wistar rats. In male rats both catechol oestradiol and catechol oestrone significantly increased the plasma concentration of LH, and catechol oestradiol but not catechol oestrone significantly increased the plasma concentration of prolactin and decreased the pituitary concentration of LH. The parent oestrogens, oestradiol-17β and oestrone, had no effect on plasma LH concentrations, but both increased significantly the plasma concentration of prolactin, and oestrone but not oestradiol-17β increased the pituitary concentration of LH. In immature female rats, catechol oestradiol inhibited the surge of LH and the increase in uterine weight induced by injecting pregnant mare serum gonadotrophin (PMSG). The injection of oestrone induced an increase in the plasma concentration of LH which was about nine times greater than that produced by oestradiol-17β. There were no significant differences in the effects of these steroids on plasma prolactin concentration. These results (i) confirm that in the immature male rat catechol oestrogens can stimulate LH release and show that catechol oestradiol can increase prolactin release, (ii) show that catechol oestradiol can inhibit the stimulatory effects of PMSG on LH release and uterine weight in the immature female rat, and (iii) demonstrate that oestrone can stimulate LH release in the immature female rat. J. Endocr. (1984) 103, 317-325

The relationship between prolactin, dehydroepiandrosterone sulphate and testosterone in normally menstruating females

1985 ◽  
Vol 109 (2) ◽  
pp. 173-175 ◽  
Author(s):  
N. C. Wathen ◽  
L. Perry ◽  
S. Hodgkinson ◽  
T. Chard
Keyword(s):  
Menstrual Cycle ◽  
Inverse Relationship ◽  
High Serum ◽  
Serum Prolactin ◽  
Dehydroepiandrosterone Sulphate ◽  
Blood Samples ◽  
Normal Women ◽  
The Relationship ◽  
Circulating Levels

Abstract. Circulating levels of prolactin, dehydroepiandrosterone sulphate (DHEAS) and testosterone (T) were measured in single blood samples from 115 normal women throughout the menstrual cycle. There was an inverse relationship between prolactin and both DHEAS and T. Subjects with high serum prolactin levels had significantly lower levels of DHEAS and T.

scholarly journals Alcohol Alters Luteinizing Hormone Secretion in Immature Female Rhesus Monkeys by a Hypothalamic Action

Endocrinology ◽  
2004 ◽  
Vol 145 (10) ◽  
pp. 4558-4564 ◽  
Author(s):  
Gregory A. Dissen ◽  
Robert K. Dearth ◽  
H. Morgan Scott ◽  
Sergio R. Ojeda ◽  
W. Les Dees
Keyword(s):  
Rhesus Monkeys ◽  
Sucrose Solution ◽  
Hormone Secretion ◽  
Luteinizing Hormone Secretion ◽  
Immature Female ◽  
Blood Samples ◽  
Female Rhesus ◽  
Lh Release ◽  
Lh Releasing Hormone ◽  
Lh Secretion

Abstract We determined whether the effect of alcohol (ALC) to suppress LH secretion in immature female monkeys is due to a hypothalamic or pituitary site of action. Beginning at 20 months of age, four monkeys received a single intragastric dose of ALC (2.4 g/kg), and four monkeys received an equal volume of a saline/sucrose solution daily until they were 36 months old. For the hypothalamic response test, two basal samples (3.5 ml) were collected at 15-min intervals via the saphenous vein, and then N-methyl-d-l-aspartic acid (NMA; 20 mg/kg) was given iv and four more blood samples collected. Three weeks later, this protocol was repeated except LH-releasing hormone (LHRH) (5 μg/kg) was used to test pituitary responsiveness. NMA or LHRH was administered 3 h after the ALC. After the pituitary challenge, each monkey was ovariectomized and 6 wk later, implanted with an indwelling subclavian vein catheter. Blood samples were drawn every 10 min for 8 h to assess effects of ALC on post-ovariectomy LH levels and the profile of LH pulsatile secretion. The hypothalamic challenge showed NMA stimulated LH release in control monkeys, an action that was blocked by ALC. The pituitary challenge revealed that LHRH stimulated LH release equally well in control and ALC-treated monkeys. A post-ovariectomy rise in LH was observed in both groups, but levels were 45% lower in ALC-treated monkeys. This reduction was attributed to an ALC-induced suppression of both baseline and amplitude of pulses. Results demonstrate that the ALC-induced suppression of LH in immature female rhesus monkeys is due to an inhibitory action of the drug at the hypothalamic level.

Sign in / Sign up

Export Citation Format

Share Document