Effect of continuous infusion of gonadotrophin-releasing hormone in ewes at different times of the year

Shareha, A. M.; Ward, W. R.; Birchall, Kathleen

doi:10.1530/jrf.0.0460331

Cited by 22 publications

(11 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The results also confirm that the CL formed fails to secrete progesterone in amounts equivalent to those seen during the luteal phase of the normal oestrous cycle Haresign et al, 1975;Shareha et al, 1976). Treatment with CB 154 with concomitant reduction in plasma levels of prolactin did not affect the basal plasma levels of LH or FSH, or the occurrence of ovulation, confirming previous observations when CB 154 was given to ewes during the oestrous cycle (Niswender, 1974) or during anoestrus when ovulation was induced by treatment with oestradiol benzoate (R. B.…”

Section: Discussionsupporting

confidence: 65%

“…Multiple injections of LH-RH and infusion of LH-RH (Shareha et al, 1976) appear to release amounts of LH similar to those found during the normal LH discharge in the oestrous cycle. Further, in the present study it is apparent that the occurrence of ovulation is not dependent on the amount of LH released in response to LH-RH treatment.…”

Section: Discussionsupporting

confidence: 51%

“…While ovulation has been induced by single or multiple injections or infusions of LH-RH in seasonally anoestrous ewes, the resulting CL fails to secrete normal amounts of progesterone (Crighton, Foster, Haresign, Haynes & Lamming, 1973;Crighton, Foster, Haresign & Scott, 1975;Haresign, Foster, Crighton, Haynes & Lamming, 1975;Shareha, Ward & Birchall, 1976). It was originally suggested that this was due to an inadequate release of LH at the time of ovulation .…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Effect of suppression of plasma prolactin on ovulation, plasma gonadotrophins and corpus luteum function in LH-RH-treated anoestrous ewes

McNeilly¹,

Land²

1979

Reproduction

View full text Add to dashboard Cite

Nineteen Scottish Blackface ewes were given LH-RH (3 X 30 micrograms i.v., 90-min intervals) during anoestrus when prolactin levels were elevated. Plasma levels of prolactin were suppressed with CB 154 (twice daily, i.m.) on Days -5 to 0 (N = 5), 0 to +5 (N = 5) or -5 to +5 (N = 5) around the day of LH-RH treatment (Day 0). Control animals (N = 4) received saline on Days -5 to +5. Nine animals ovulated forming corpora lutea as judged by laparoscopy on Day +7. No difference in FSH or LH levels was found between treatments and ovulations occurred equally in all treatment groups. Progesterone levels were less than ng/ml in all animals up to Day 14. It is concluded that short-term suppression of prolactin does not affect the incidence of ovulation or corpus luteum progesterone production in LH-RH-treated anoestrous ewes.

show abstract

Section: Discussionsupporting

confidence: 65%

Section: Discussionsupporting

confidence: 51%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of suppression of plasma prolactin on ovulation, plasma gonadotrophins and corpus luteum function in LH-RH-treated anoestrous ewes

McNeilly¹,

Land²

1979

Reproduction

View full text Add to dashboard Cite

show abstract

“…Similar biphasic responses to infusions of LH-RH have been observed in man (Bremner & Paulsen, 1974) and to a certain extent in the rat , and have been proposed as evidence for the existence of two pools of LH. In the rat, LH levels decline after a few hours of infusion, and a similar termination of responsiveness to infused LH-RH has been observed in the sheep, though a biphasic response was not described (Chakraborty, Adams, Tarnavsky & Reeves, 1974;Symons, Cunningham & Saba, 1974;Shareha, Ward & Birchall, 1976). Such a decrease during the course of the infusions in the present study on the guinea-pig was not observed, possibly because of the relatively short period of infusion.…”

Section: Discussionsupporting

confidence: 75%

Luteinizing Hormone Responsiveness to Luteinizing Hormone Releasing Hormone in the Adult Guinea-Pig: Direct Ovarian Involvement

Haar¹

1978

Journal of Endocrinology

View full text Add to dashboard Cite

The effects of intravenous injection of synthetic luteinizing hormone releasing hormone (LH-RH) on the release of LH and FSH have been studied in the adult guinea-pig. In all the experiments the secretion of FSH was apparently unaffected by administration of LH-RH. The release of LH was log dose-dependent over the range 0\m=.\5\p=n-\50 \ g=m\ g LH-RH.During the female cycle, the maximum increment in the concentration of LH after a single i.v. injection of 0\m=.\5 \g=m\g LH-RH decreased progressively from day 1 to day 13. Double or triple injections of 1 \g=m\g LH-RH at 1 h intervals produced no potentiation on day 3 but progressively greater LH responses occurred on days 7, 10 or 13 of the oestrous cycle. Ovariectomy immediately before the first injection of LH-RH on day 7 blocked the potentiated response to subsequent injections, whereas ovariectomy immediately before the second injection still permitted this potentiation. These results suggest that there is direct ovarian involvement in the potentiated response to LH-RH observed during the later part of the guinea-pig oestrous cycle.Infusion of LH-RH (1 \ g=m\ g over 200 min) produced a potentiated release of LH in female guinea-pigs on day 7 (but not on day 3) of the oestrous cycle after a delay of 1\m=.\5h. It is proposed that there are two 'pools' of LH in the pituitary gland of the female guinea-pig and that the second pool is 'activated' consequent upon previous hypophysial stimulation of secretion from an ovary containing adequately developed follicles.Luteinization or ovulation can be induced in guinea-pigs by two injections of LH-RH administered 1 h apart after day 7 of the cycle ( . T. Donovan, personal communication). Animals were therefore treated on days 7, 10 or 13 with two i.v. injections of 1 µg LH-RH (2 µg/ml) each flushed in with 0-5 ml physiological saline) 65 min apart. Blood samples were collected 10, 20 and 30 min before and 7, 15, 25, 35, 45 and 55 min after the first injection and 7, 15, 25, 35, 45, 55, 70, 85, 100, 115, 130, 145, 160, 175 and 190 min after the second injection of LH-RH.

show abstract

“…It is particularly evident during the midcycle surge period, where continued GnRH did not prevent the rapid fall of LH occurring at this time in the normal menstrual cycle, and in the ovariec¬ tomized animals where FSH levels unexpectedly declined to half the control values during the infusion. Such decreased gonadotrophin responsiveness to continued stimulation by GnRH is not limited to the rhesus monkey for it has been reported in a number of other species (Jewelewicz et al 1977;Piper et al 1975;Gumming et al 1972;Shareha et al 1976;Chakraborly et al 1974;Libertun et al 1974). These results must raise the possibility for the existence of other active pituitary controlling mechanisms.…”

Section: Discussionmentioning

confidence: 77%

PITUITARY AND OVARIAN HORMONAL RESPONSE TO 48 h GONADOTROPHIN RELEASING HORRMONE (GnRH) INFUSIONS IN FEMALE RHESUS MONKEYS

Ferin

Bogumil

Drewes

et al. 1978

Acta Endocrinologica

View full text Add to dashboard Cite

The effects of prolonged gonadotrophin-releasing hormone (GnRH) infusions on LH, FSH, oestrogens and progesterone secretion were studied in female rhesus monkeys at various times of the menstrual cycle and after castration. GnRH was infused at the rate of 15 \g=m\g/h for 48 h. This resulted in mean peripheral GnRH levels of 398 \m=+-\ 31.5 pg/ml (\m=+-\se) as measured by radioimmunoassay. As expected the pattern of gonadotrophin responses to GnRH varied considerably with the phase of the menstrual cycle. The largest LH increase was seen during the late follicular phase (6-fold over baseline), with a 3-fold increase during the luteal phase and a 2-fold one during the early follicular phase and in the period following the LH surge. Significant FSH increases (4-fold) were seen only during the follicular phase. Oestrogens increased about 2-fold within 4 h of the start of the infusion during the early follicular phase. In the late follicular phase and during the LH surge, they declined within 24 and 1 h, respectively. Large progesterone increases were seen only during the luteal phase. Of special interest is the fact that the increase in gonadotrophin secretion could not be maintained for the entire duration of the experiment even though GnRH continued to be infused at rates sufficient to elicit initial increases of several fold over baseline. Gonadotrophin release declined 4\p=n-\28 h after the initial stimulation. A further decrease below pre-infusion

show abstract

Effect of continuous infusion of gonadotrophin-releasing hormone in ewes at different times of the year

Cited by 22 publications

References 27 publications

Effect of suppression of plasma prolactin on ovulation, plasma gonadotrophins and corpus luteum function in LH-RH-treated anoestrous ewes

Effect of suppression of plasma prolactin on ovulation, plasma gonadotrophins and corpus luteum function in LH-RH-treated anoestrous ewes

Luteinizing Hormone Responsiveness to Luteinizing Hormone Releasing Hormone in the Adult Guinea-Pig: Direct Ovarian Involvement

PITUITARY AND OVARIAN HORMONAL RESPONSE TO 48 h GONADOTROPHIN RELEASING HORRMONE (GnRH) INFUSIONS IN FEMALE RHESUS MONKEYS

Contact Info

Product

Resources

About