Patterns of Pituitary Release and Cranial Output of LH and Prolactin in Ovariectomized Ewes

Butler, Walter; Malven, P.V.; Willett, L. B.; Bolt, D. J.

doi:10.1210/endo-91-3-793

Cited by 117 publications

(47 citation statements)

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“…As found by others (Butler, Malven, Willett & Bolt, 1972;Reeves, O'Donnell & Denorscia, 1972;Diekman & Malven, 1973), shortly after ovariectomy the control anoestrous ewes had plasma LH concentrations, pulse amplitudes and frequencies higher than those reported in entire anoestrous ewes (Martensz, Baird, Scaramuzzi & Van Look, 1976;Scaramuzzi & Baird, 1977). If the pulsatile release of LH reflects the pulsatile release of LH-RH (Lincoln & Short, 1980) Goodman & Legan, 1980), could in part reflect a reduction in hypothalamo-pituitary activity independent of the influence of ovarian hormones, as well as an increased inhibitory effect of oestrogen on LH release (Legan, Karsch & Foster, 1977).…”

Section: Discussionmentioning

confidence: 69%

Suppressed release of LH in ovariectomized post-partum ewes

Wright¹,

Stelmasiak²,

Anderson³

1983

Reproduction

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Summary. The patterns of LH release were studied in 5 ewes, ovariectomized when 3 days post partum, at 4, 14, 33, 47 and 61 days after ovariectomy. These patterns were compared with those in 4 seasonally anoestrous (control) ewes ovariectomized and sampled at the same times. In the control ewes regular pulsatile release of LH was apparent 4 days after ovariectomy: plasma LH concentrations and LH pulse frequencies, but not pulse amplitudes, then declined. In the post-partum ewes all indices of LH release were lower than those in the control ewes at 4 days after ovariectomy, but then they increased: pulse amplitude was greater (P < 0\m=.\05)at 14 days after ovariectomy, and plasma LH concentrations were greater (P < 0\m=.\05,0\m=.\01) at 14 and 33 days than in control ewes. These results indicate that the hypothalamo\p=n-\ pituitary axis of lactating ewes has a reduced capacity to release LH for only a short period after ovariectomy early in the post-partum period. This probably reflects the time needed for recovery from the inhibitory effects of ovarian and placental hormones, and may reflect reduced secretion of LH-RH.

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Section: Discussionmentioning

confidence: 69%

Suppressed release of LH in ovariectomized post-partum ewes

Wright¹,

Stelmasiak²,

Anderson³

1983

Reproduction

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“…Recently, Palmer, Phillips, Howland & Ibrahim (1972), Fell, Beck, Brown, Catt, Cumming & Goding (1972) and Butler, Malven, Willett & Bolt (1972) have presented some evidence which indicates that episodic LH releases occur in anoestrous and anovulatory ewes. Progesterone has been found to be at basal levels throughout anoestrus with some elevations occurring before the first behavioural oestrus of the breeding season (Thorburn et al, 1969).…”

Section: Introductionmentioning

confidence: 99%

Luteinizing Hormone, Oestrogen and Progesterone Levels in Peripheral Serum of Anoestrous and Cyclic Ewes as Determined by Radioimmunoassay

Yuthasastrakosol¹,

Palmer²,

Howland³

1975

Reproduction

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Summary. Jugular vein blood was collected daily from four mature ewes throughout anoestrus and the first oestrous cycle of the breeding season until 4 days after the second oestrus. The levels of oestrogen, progesterone and LH were determined by radioimmunoassay. There were fluctuations in the LH level throughout most of the observed anoestrous period with a mean \ m=+-\ S.E. value of 2\m=.\3\ m=+-\ 0\m=.\9 ng/ml. High LH values of 20\m=.\0, 41\m=.\2and 137\m=.\5 ng/ml were observed in three ewes on Day \m=-\24of anoestrus. A brief minor rise in progesterone level was also observed around this period. Progesterone levels were consistently low (0\m=.\11 \ m=+-\ 0 \ m= . \ 0 1 ng/ml) before Day \m=-\25of anoestrus. A major rise occurred on Day \m=-\12 of anoestrus and this was followed by patterns similar to those that have been previously reported for the oestrous cycle of the ewe. Random fluctuations of oestrogens deviating from a mean level of 4\m=.\40 \ m=+-\ 0\m=.\1 pg/ml were observed during anoestrus and the mean level during the period from the first to the second oestrus was 5\m=.\2\ m=+-\ 0\m=.\3 pg/ml. A wel l \x=req-\ defined peak of 13\m=.\3\ m=+-\ 0\m=.\7 pg/ml was seen in all ewes on the day of the second oestrus. Results of the present study suggest that episodic releases of LH occur during anoestrus and periods of low luteal activity. The fluctuations in LH levels, as observed during the period of low luteal activity, i.e. before Day \m=-\25 of anoestrus, were less pronounced during the periods of high luteal activity. The view that luteal activity precedes the first behavioural oestrus of the breeding season is supported.

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“…It has long been known that LH concentrations increase after ovariectomy in the ewe (Arendarcik & Maracek, 1968;Roche, Foster, Karsch & Dziuk, 1970;Reeves, O'Donnell & Denorscia, 1972). However, data on the changes in pulsatile release of LH after ovariectomy are limited (Butler, Malvern, Willett & Bolt, 1972;Reeves et al, 1972;Diekman & Malvern, 1973;Wright, Stelmasiak & Anderson, 1983). The effects of season and time after ovariectomy require further investigation to assess the effects of steroid-dependent and -independent effects on changes in gonadotrophin secretion with season. In any long-term study of (Pelletier, Kann, Doláis & Rosselin, 1968), with the modifications recently described (Pelletier, Gamier, de Reviers, Terqui & Ortavant, 1982).…”

Section: Introductionmentioning

confidence: 99%