CHANGES IN PLASMA LEVELS OF PROLACTIN AND LH INDUCED BY LUTEOLYTIC OR LUTEOTROPHIC TREATMENT IN INTACT CYCLING SHEEP AFTER SECTION OF THE PITUITARY STALK

1973 ◽  
Vol 73 (4) ◽  
pp. 625-634 ◽  
Author(s):  
G. Kann ◽  
R. Denamur
Keyword(s):  
Pituitary Gland ◽  
Plasma Levels ◽  
Limit Of Detection ◽  
Oestrous Cycle ◽  
The Other ◽  
Pituitary Stalk ◽  
Similar Treatment ◽  
Luteal Regression ◽  
Gonadotrophin Secretion ◽  
Major Increase

ABSTRACT Oestradiol has been shown to cause either premature luteal regression or prolonged luteal maintenance depending on whether it is administered early or late in the oestrous cycle. Although these effects are not observable in the absence of the uterus, it was considered desirable to examine the possibility that the pituitary gland as well as the uterus may be involved in this phenomenon. Accordingly, plasma LH and prolactin concentrations were studied in sheep treated with oestradiol from day 3 (luteotrophic action) or day 11 (luteolytic action) with and without pituitary stalk section. Plasma LH fell below the limit of detection (0.3 ng/ml) in the plasma of sheep after pituitary stalk section, whether or not oestradiol had been administered. In the intact ewe, oestradiol given from day 3 resulted in luteal maintenance associated with a significant increase in the secretion of plasma LH and prolactin. However, similar treatment in the stalk sectioned ewe also resulted in luteal maintenance without any major increase in gonadotrophin secretion. On the other hand, when oestradiol was given from day 11, there was no evidence either from the intact or the stalk sectioned sheep that the pituitary contributed to the luteolytic action of oestradiol may possibly have a pituitary component, the luteolytic action is probably mediated solely by the oestrogenic action on the uterus.

LUTEOLYTIC EFFECTS OF OESTRADIOL AFTER HYPOPHYSECTOMY OR PITUITARY STALK SECTION IN CYCLING SHEEP

1973 ◽  
Vol 73 (4) ◽  
pp. 635-642 ◽  
Author(s):  
R. Denamur ◽  
G. Kann
Keyword(s):  
Pituitary Gland ◽  
Life Span ◽  
Corpus Luteum ◽  
Direct Action ◽  
The Other ◽  
Pituitary Stalk ◽  
Relative Importance ◽  
Luteal Regression ◽  
Other Hand ◽  
Oestradiol Benzoate

ABSTRACT Experiments were carried out with a view to determining the relative importance of the pituitary gland and the uterus for the luteolytic action of oestradiol in the cycling ewe. The influence of the pituitary was modified by stalk section or hypophysectomy and that of the uterus by hysterectomy. Oestradiol (0.5 mg twice daily) caused an increase in ghe life-span of the corpus luteum (CL) if treatment began on day 3 of the cycle, and a decrease when injections commenced on days 9 or 11. Pituitary stalk sections performed on days 3 or 11 caused little change in CL weight on day 14. However, in either case, oestradiol administration from day 11 resulted in a large fall in CL weight, indicating that intact pituitary connections to the hypothalamus were not essential for the luteolytic action of oestradiol. Luteal regression following hypophysectomy on day 11 was accelerated by oestradiol benzoate injected from day 11. On the other hand, hysterectomy on day 11 always resulted in maintenance of the CL to day 20, whether or not stalk section or oestradiol administration had taken place. This indicated that the presence of the uterus was essential for the luteolytic effects of oestradiol. These experiments show that the luteolytic properties of oestradiol reflect mainly a direct action of this hormone on the uterus.

THE ROLE OF THE PITUITARY GLAND IN IMPLANTATION IN THE MOUSE: DELAY OF IMPLANTATION BY HYPOPHYSECTOMY AND NEURODEPRESSIVE DRUGS

1969 ◽  
Vol 43 (2) ◽  
pp. 225-235 ◽  
Author(s):  
B. M. BINDON
Keyword(s):  
Pituitary Gland ◽  
Early Pregnancy ◽  
Single Injection ◽  
Hormone Replacement ◽  
Oestrous Cycle ◽  
The Other ◽  
Optimum Conditions ◽  
Delayed Implantation ◽  
Long Acting

SUMMARY The optimum conditions for delay of implantation by hypophysectomy and neurodepressive agents are described. Hypophysectomy on day 1 without hormone replacement was followed by retarded development and subsequent degeneration of zygotes. Viability of blastocysts was maintained under these conditions by a single injection of a long-acting progestagen on day 1. Hypophysectomy at intervals beginning late on day 3 indicated that implantation is initiated by pituitary activity in the several hours around midnight of this day. In animals induced to ovulate and copulate by exogenous gonadotrophin injections, the corresponding time of pituitary activity was delayed by approximately 8 hr. This delay could not be explained solely on the basis of altered times of ovulation. It is evident that the events of early pregnancy do not follow the normal physiological pattern under these conditions, and caution should be exercised in utilizing such animals. Of five neurodepressive agents examined, only trifluoperazine effectively delayed implantation. The effect of this substance injected at various times on day 3 of pregnancy suggests that implantation in the mouse is initiated by neurally regulated pituitary activity between 16.00 and 24.00 hr. on this day. Comparison with the mechanism of ovulation indicates that ovulation and implantation are regulated by separate hypothalamic-pituitary events, one peculiar to the oestrous cycle, the other to early pregnancy.

Effect of stress on tissue and plasma levels of immunoreactive β-endorphin in ovariectomized rats primed with oestrogen and progesterone

1984 ◽  
Vol 100 (3) ◽  
pp. 277-280 ◽  
Author(s):  
G. K. Hulse ◽  
G. J. Coleman
Keyword(s):  
Pituitary Gland ◽  
Plasma Levels ◽  
Anterior Pituitary ◽  
Sesame Oil ◽  
Anterior Pituitary Gland ◽  
Oestrous Cycle ◽  
Ovariectomized Rats ◽  
Neurointermediate Lobe ◽  
Pituitary Tissue

ABSTRACT The aim of this study was to investigate the effect of oestrogen and progesterone on levels of immunoreactive β-endorphin (Ir-β-EP) in the hypothalamus, anterior pituitary gland, neurointermediate lobe and plasma under normal conditions and conditions of stress. The injection of oestrogen + progesterone into ovariectomized rats increased Ir-β-EP levels in extracts of anterior pituitary tissue and in plasma, under both normal and stressed conditions. Exposure to a stress reduced the content of anterior pituitary Ir-β-EP in ovariectomized rats treated with oestrogen + progesterone and also with sesame oil. Such treatment only resulted in increments in plasma Ir-β-EP in oil-treated but not in oestrogen + progesterone-treated overiectomized rats. It was concluded (1) that oestrogen and progesterone are involved in the regulation of resting levels of anterior pituitary Ir-β-EP during the rat oestrous cycle, (2) that stress reduces levels of anterior pituitary Ir-β-EP and (3) that increased levels of plasma oestrogen + progesterone inhibit plasma Ir-β-EP increments which normally accompany exposure to stress. J. Endocr. (1984) 100, 277–280

scholarly journals Gonadotrophin storage patterns in the ewe during the oestrous cycle or after long-term treatment with a GnRH agonist

1998 ◽  
Vol 156 (1) ◽  
pp. 149-157 ◽  
Author(s):  
C Taragnat ◽  
A Bernier ◽  
J Fontaine
Keyword(s):  
Pituitary Gland ◽  
Gnrh Agonist ◽  
Term Treatment ◽  
Oestrous Cycle ◽  
Pituitary Cells ◽  
Double Immunostaining ◽  
Gonadotrophin Secretion ◽  
Long Term Treatment ◽  
Lh Cells

The storage pattern of gonadotrophins in the ewe pituitary was investigated during the oestrous cycle and after desensitization to GnRH using long-term treatment with a GnRH agonist, buserelin. Oestrous cycles in ewes were synchronized with progestagen sponges. Animals were allocated to two experiments. In the first, ewes were killed 36 h (before the preovulatory surge, n = 4), 48 h (end of the preovulatory surge, n = 5), 72 h (post-ovulation, n = 4) and 240 h (luteal phase, n = 3) after sponge removal. In the second experiment, another progestagen sponge was inserted in ewes 84 h after removal of the first sponge. Four ewes were infused continuously with buserelin (50 micrograms/day) for 15 days before killing. A further four ewes received no buserelin (controls). Pituitaries were collected and processed for immunocytochemistry to detect monohormonal (LH or FSH) and multihormonal (LH/FSH) cells. The percentages of LH or FSH immunoreactive cells in the pituitary were lower at the end of the preovulatory surge (7.4 +/- 0.3% and 1.2 +/- 0.3% respectively) compared with the other stages (11.4 +/- 0.5% and 5.4 +/- 0.7% respectively). Analysis of dual immunostaining showed the existence of monohormonal cells for LH and multihormonal cells (LH/FSH). No monohormonal cell for FSH was detected except at the end of the preovulatory surge when a few monohormonal FSH cells appeared (0.1 +/- 0.01% of pituitary cells). The percentage of monohormonal LH cells in the pituitary gland was similar in all studied stages of the oestrous cycle, whereas the percentage of multihormonal cells was lower at the end of the surge. In agonist-treated ewes, the percentages of LH or FSH immunoreactive cells (5.3 +/- 0.5% and 1.5 +/- 0.8% respectively) were decreased compared with controls (9.4 +/- 1% and 7.5 +/- 1.1% respectively). Analysis of the double immunostaining revealed a few monohormonal FSH cells (0.2 +/- 0.01% of pituitary cells) in agonist-treated ewes but not in controls. The percentage of monohormonal LH cells in the pituitary gland increased from 1.9 +/- 0.2% in controls to 3.8 +/- 0.3% in agonist-treated ewes, whereas multihormonal cells dropped from 7.5 +/- 1.1% to 1.3 +/- 0.7%. Our data suggest, therefore, that multihormonal cells contribute to gonadotrophin secretion, either during the preovulatory surge of the oestrous cycle or during the 'flare-up' effect initially induced by a GnRH agonist. Moreover, the appearance of monohormonal FSH cells in some conditions reflects a differential regulation of LH and FSH.

REPETITIVE TREATMENT WITH GONADOTROPHIN RELEASING FACTOR OR A LONG-ACTING ANALOGUE UPON GONADOTROPHIN SECRETION IN THE FERRET

1981 ◽  
Vol 90 (2) ◽  
pp. 275-283
Author(s):  
B. GLEDHILL ◽  
B. T. DONOVAN
Keyword(s):  
Intravenous Injection ◽  
Plasma Levels ◽  
Sampling Period ◽  
The Other ◽  
Single Intravenous Injection ◽  
Three Samples ◽  
Gonadotrophin Secretion ◽  
Long Acting ◽  
Lh Releasing Hormone ◽  
Very High

The changes in plasma levels of LH and FSH were examined after treatment of intact and ovariectomized female ferrets with a long-acting analogue of gonadotrophin releasing factor (Gn-RF) (d-Ser(But)6-LH-releasing hormone(1–9)-nonapeptide ethylamide; Hoe 766) either as a single intravenous injection or daily for 6 days. The responses were compared with those induced by daily injections of Gn-RF or 0·9% NaCl (w/v). Treatment with Gn-RF consistently induced rises in both LH and FSH release with peak levels of both hormones being reached 20 min after injection and being of similar size from day to day in individual animals. Thereafter, the gonadotrophin levels declined rapidly to approach basal values by the end of each sampling period. Treatment with Hoe 766, however, produced very high values on day 1 of treatment, with LH being raised for 10–12 and FSH for up to 24 h. Subsequent injections, on the other hand, produced an abbreviated LH response of similar size to that induced by Gn-RF and little, if any, FSH response. In ovariectomized ferrets, Hoe 766 induced a variable LH response and little FSH response at any time. In addition, basal FSH levels in the first three samples taken on each day from day 2 onwards tended to decline markedly in all of the Hoe 766-treated animals, an effect not seen in Gn-RF or 0·9% NaCl-treated controls.

Regulation of the seasonal cycle of β-endorphin and ACTH secretion into the peripheral blood of rams

1990 ◽  
Vol 124 (3) ◽  
pp. 443-454 ◽  
Author(s):  
E. Ssewannyana ◽  
G. A. Lincoln ◽  
E. A. Linton ◽  
P. J. Lowry
Keyword(s):  
Plasma Concentration ◽  
Pituitary Gland ◽  
Plasma Levels ◽  
Seasonal Cycle ◽  
Plasma Concentrations ◽  
Pituitary Hormones ◽  
Similar Treatment ◽  
Corticotrophin Releasing Factor ◽  
Differential Control ◽  
Autumn And Winter

ABSTRACT In a group of 12 adult Soay rams living outdoors near Edinburgh there was a conspicuous seasonal cycle in the peripheral plasma concentrations of β-endorphin, ACTH and cortisol. The concentration of all three hormones increased 5- to 20-fold from winter to summer; the seasonal maximum occurring from May to July for ACTH and cortisol and in August for β-endorphin. At the peak of the cycle the ratio of β-endorphin to N-acetyl-β-endorphin was 22:1. The regulation of the seasonal cycle was investigated in a series of five experiments involving treatments with arginine vasopressin (AVP), corticotrophin-releasing factor (CRF) and the synthetic glucocorticoid, dexamethasone. Injection of AVP i.v. induced a dose-dependent increase in the plasma concentration of β-endorphin (AVP doses of 0, 0·07, 0·33 and 1·67 μg/kg). AVP (0·33 μg/kg) and CRF (1·67 μg/kg) given alone or in combination (equimolar doses), induced an increase in the plasma concentrations of β-endorphin and ACTH in spring, summer, autumn and winter, and produced a synergistic response when given together. The responses varied with season and were greatest in summer and autumn at the time of the seasonal increase in endogenous secretion. Dexamethasone injected i.v. at 68·04 μg/kg produced a decrease in the plasma concentrations of β-endorphin and ACTH, and the responses were also greatest in summer and autumn. A similar treatment with dexamethasone blocked the AVP-induced increase in the plasma levels of β-endorphin, indicating an action of dexamethasone on the pituitary gland. Administration of ACTH (0·33 μg/kg; i.v.) to rams pretreated with dexamethasone stimulated an increase in the plasma concentration of cortisol; this response varied with season, being greatest in spring at the time of the peak in the seasonal cycle in cortisol secretion. The administration of β-endorphin (0·33 pg/kg) failed to induce an increase in the plasma levels of cortisol at any season. Analysis of the hormone profiles in the control rams based on blood samples collected every 10 min for 8 h revealed pulsatile variations in the plasma concentration of ACTH; some of the spontaneous ACTH peaks were correlated with β-endorphin peaks. From these results in the Soay ram, we conclude that β-endorphin and ACTH are co-secreted from the pituitary gland following stimulation by AVP and CRF, and that adrenal glucocorticoids stimulated by ACTH can act in a negative feedback role at the level of the pituitary gland to inhibit the release of both β-endorphin and ACTH. These acute studies indicate a parallel control of β-endorphin and ACTH at all stages of the seasonal cycle, and a seasonal change in the secretion of AVP and CRF from the hypothalamus may constitute the 'drive' to the seasonal cycle in both β-endorphin and ACTH. There was, however, a notable difference in the timing of the seasonal cycle in β-endorphin compared with that of ACTH, which indicates some form of differential control of these two pituitary hormones. Journal of Endocrinology (1990) 124, 443–454

SECRETION DE LA PROGESTERONE PAR LES CORPS JAUNES DE LA BREBIS APRES HYPOPHYSECTOMIE, SECTION DE LA TIGE PITUITAIRE ET HYSTERECTOMIE

1966 ◽  
Vol 52 (1) ◽  
pp. 72-90 ◽  
Author(s):  
R. Denamur ◽  
J. Martinet ◽  
R. V. Short
Keyword(s):  
Pituitary Gland ◽  
Corpus Luteum ◽  
Secretory Activity ◽  
Oestrous Cycle ◽  
Pituitary Stalk ◽  
Rapid Decline ◽  
Corpora Lutea ◽  
List Type ◽  
Normal Cycle ◽  
Progesterone Secretion

ABSTRACT The purpose of these experiments was to investigate the part played by the pituitary gland and the uterus in the control of the corpus luteum in the sheep. Six experiments were carried out, as follows: Hypophysectomy early and late in the oestrous cycle. Hypophysectomy on days 2–5 allowed the corpus luteum to continue secreting normal amounts of progesterone for up to 9 days, but thereafter the secretion declined. Hypophysectomy on days 9–10 caused the progesterone secretion to fall within 4 days. Thus it seems that the corpus luteum has a limited functional life span, and it normally requires the presence of a pituitary luteotrophin during the second half of the oestrous cycle if it is to secrete normally for 15 days. Pituitary stalk section early and late in the oestrous cycle. Regardless of the time of stalk section, the corpus luteum behaves as it would during a normal cycle. Thus pituitary stalk section does not produce the same effect as hypophysectomy, and seems to allow the severed pituitary gland to continue secreting luteotrophin. Hypophysectomy and hysterectomy carried out simultaneously early in the cycle. The results were similar to those in 1, progesterone secretion having declined significantly by days 12–15. This confirms that the declining secretory activity is due to a deficiency of pituitary luteotrophin, and not to any uterine luteolytic effect in this experiment. Pituitary stalk section and hysterectomy carried out simultaneously early in the cycle. In striking contrast to 3, some corpora lutea were still secreting progesterone normally on day 18. This shows once again that the isolated pituitary gland can continue to secrete luteotrophin. The different responses in this experiment and 2 emphasise the fact that the uterine luteolytic effect is normally dominant to the pituitary luteotrophic stimulus. Thus it would be impossible to demonstrate luteotrophic activity if the uterus were still present. Hysterectomy carried out at mid cycle, followed by hypophysectomy 20–30 days later. Whilst hysterectomy alone prolongs the secretory activity of the corpus luteum, subsequent hypophysectomy results in a rapid decline in progesterone secretion, commencing 48 hours after the operation. Thus the corpora lutea prolonged by hysterectomy, unlike those of the normal cycle, require daily pituitary luteotrophin secretion for their continued existence. Hysterectomy carried out at mid cycle, followed by pituitary stalk section 20–30 days later. Unlike 5, stalk section allows the corpora lutea to continue to secrete progesterone in large amounts for at least 15 days after the operation. This experiment, together with 2 and 4, once again emphasises that the stalk-sectioned pituitary gland can continue to secrete luteotrophin, at least for a time. These experiments therefore support the view that the cyclical corpus luteum of the sheep is under a dual control. There is a pituitary luteotrophin, whose secretion continues after stalk section, and a uterine luteolysin that is dominant to the luteotrophic stimulus, and can still function normally after pituitary stalk section. The fact that the corpus luteum of the hysterectomised animal cannot function for more than about 15 days after stalk section suggests that the luteotrophic stimulus may be complex, possibly envolving more than one hormone.

PLASMA AND PITUITARY LUTEINIZING HORMONE AND PERIPHERAL PLASMA OESTRADIOL CONCENTRATIONS IN THE NORMAL OESTROUS CYCLE OF THE RAT AND AFTER EXPERIMENTAL MANIPULATION OF THE CYCLE

1972 ◽  
Vol 53 (1) ◽  
pp. 17-30 ◽  
Author(s):  
F. NAFTOLIN ◽  
K. BROWN-GRANT ◽  
C. S. CORKER
Keyword(s):  
Luteinizing Hormone ◽  
Plasma Levels ◽  
Experimental Manipulation ◽  
Oestrous Cycle ◽  
Postnatal Life ◽  
Normal Cycle ◽  
Rapid Fall ◽  
Major Increase ◽  
Plasma Oestradiol

SUMMARY Plasma and pituitary luteinizing hormone (LH) concentrations were measured by radioimmunoassay at different stages of the normal 4- and 5-day oestrous cycle of rats. Plasma levels were low except between the afternoon of pro-oestrus and the morning of oestrus when levels were high but variable. Pituitary LH content and concentration were less consistent but averaged values showed a steady rise from a low level after ovulation to a peak on the afternoon of pro-oestrus, and a rapid fall that evening when plasma levels rose rapidly. No significant differences were observed in plasma LH between 4- and 5-day cycles; in particular there was no reduction at metoestrus or dioestrus-1 or increase on the evening of dioestrus-2. Plasma oestradiol was already high on the morning of dioestrus-2 in some rats and in all rats by that evening. On the morning of pro-oestrus in the 5-day cycle, plasma oestradiol was still high but somewhat lower than at the corresponding stage in the 4-day cycle. Blocking ovulation by administration of sodium pentobarbitone at prooestrus in a 4-day cycle prevented the rise in plasma LH and the fall in pituitary content. Blocking generally failed in animals whose plasma LH had reached the level of 20 ng/ml or more at the time of injection. Plasma oestradiol levels on the morning of the expected day of oestrus were higher than normal in animals in which ovulation was blocked by pentobarbitone but were below pro-oestrous values. In the anovulatory state induced by exposure to constant light no major increase in plasma LH was detected after 24 days of illumination or after 3 months exposure. Animals rendered anovulatory by injection of testosterone propionate on the 4th day of postnatal life had low plasma LH levels as adults. All three groups had a low pituitary LH content. The animals exposed to long-term light and those treated with androgen generally had plasma oestradiol concentrations below the peak levels seen on the morning of pro-oestrus in the normal cycle.

EFFECT OF FEEDING ETHINYLOESTRADIOL FOR VARIOUS PERIODS BEFORE MATING ON REPRODUCTION IN THE HAMSTER

1972 ◽  
Vol 70 (3) ◽  
pp. 582-590
Author(s):  
B. K. Davis ◽  
I. Noske ◽  
M. C. Chang
Keyword(s):  
Single Dose ◽  
Pregnancy Rate ◽  
Fertility Control ◽  
Normal Pregnancy ◽  
Oestrous Cycle ◽  
The Other ◽  
Feeding Schedule ◽  
Crown Rump Length ◽  
Essentially Normal ◽  
Effect Of Feeding

ABSTRACT Ethinyloestradiol (EO) fed for various periods before mating to female hamsters affected the timing of mating and pregnancy rate. Slight effects on ovulation, foetal-crown rump length and resorption may have occurred, but effects on implantation were not apparent among pregnant hamsters. The response observed depended upon the feeding schedule adopted: hamsters fed 2.5 mg EO in a single dose, on day 3 before mating, mated normally but had a significantly lower pregnancy rate; on the other hand, animals fed 2.5 mg EO (0.21 mg/day) over three oestrous cycles, days 14–3 before mating, showed variations in the time of mating but had an essentially normal pregnancy rate; and, a group of hamsters who received the same total amount of EO (0.63 mg/day) over one oestrous cycle, days 6–3 premating, showed untowards effects by the steroid on both the timing of mating and pregnancy rate. The implications of these results are considered in relation to fertility control.

Seasonal Fluctuations in Pituitary Gland and Plasma Levels of Gonadotropic Hormones inRana

1998 ◽  
Vol 109 (1) ◽  
pp. 13-23 ◽  
Author(s):  
Jung W. Kim ◽  
Wook-Bin Im ◽  
Han H. Choi ◽  
S. Ishii ◽  
Hyuk B. Kwon
Keyword(s):  
Pituitary Gland ◽  
Plasma Levels ◽  
Seasonal Fluctuations ◽  
Gonadotropic Hormones
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