Plasma Estrogens in Pregnant and Postpartum Mares2

Nett, T. M.; Holtan, D. W.; Estergreen, V.L.

doi:10.2527/jas1973.374962x

Cited by 87 publications

(30 citation statements)

References 16 publications

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“…As in other domestic species some of the main secretory products of the equine preovulatory follicle are oestrogens and the blood concentration of total oestrogens increases during the period of sexual receptivity (Nett, Holtan & Estergreen, 1973). Plotka, Foley, Witherspoon, Schmoller & Goetsch (1975) have shown that the concentration of unconjugated oestrogen in peripheral plasma remains unchanged at 50 pg/ml throughout the periovulatory period.…”

Section: Introductionmentioning

confidence: 95%

Changes in oestrone sulphate concentrations in peripheral plasma of Pony mares associated with follicular growth, ovulation and early pregnancy

Makawiti¹,

Allen²,

Kilpatrick³

1983

Reproduction

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Summary. A simple and rapid ( < 2 h) immunoassay method has been developed based upon a novel separation technique called LIDIA (Ligand Differentiation Immunoassay), enabling direct estimation of the concentration of oestrone sulphate in ethanolic extracts of blood plasma. An antiserum raised against oestrone-3-glucuronyl\p=n-\BSA was used which showed a higher cross-reaction with the sulphate than the glucuronide metabolite. The assay had a sensitivity of 5\m=.\2 pg/tube and acceptable inter-( < 18%) and intra-(<8\m=.\5%)assay precision. Analysis of samples of peripheral venous plasma obtained daily from Pony mares showed that the mean concentration of oestrone sulphate started to rise from a baseline value ( < 300 pg/ml) at 6 days and reached a peak ( > 850 pg/ml) at 2 days before follicular rupture as determined by rectal palpation. Progesterone concentrations only started to rise above baseline ( < 0\m=.\5 ng/ml) on the day of ovulation and reached a peak 8 days later. Analysis of samples obtained during the first 30 days of pregnancy showed that there was no increase in oestrone sulphate at the time oestrus would have been expected had the mares not conceived.

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Section: Introductionmentioning

confidence: 95%

Changes in oestrone sulphate concentrations in peripheral plasma of Pony mares associated with follicular growth, ovulation and early pregnancy

Makawiti¹,

Allen²,

Kilpatrick³

1983

Reproduction

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“…After day 60, gestagens are also produced by the placenta, and from day 150 onwards, the placenta is the only source of gestagens in the pregnant mare (Holtan et al 1991). High oestrogen concentrations in the blood of pregnant mares are found from the 4th to the 9th month of gestation (Nett et al 1973).…”

Section: Introductionmentioning

confidence: 99%

Opioidergic inhibition of luteinising hormone and prolactin release changes during pregnancy in pony mares

Aurich

Aurich²,

Parvizi³

2001

Journal of Endocrinology

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In equine species, luteinising hormone (LH) and prolactin (PRL) release are reduced throughout pregnancy but increase at foaling. The present experiments were designed to study a possible opioidergic regulation of LH and PRL release in pregnant Shetland mares (n=6). At various stages of pregnancy (days 26·4 0·6, 75·4 5·4, 171·8 2·4, 226·2 4·8, 282·7 3·4 and 319·8 2·1), mares were injected with the opioid antagonist naloxone (0·5 mg/kg body weight) and saline. The two treatments were always separated by 2 days, and mares served as their own controls. Two hours after being given naloxone and saline, mares were given the gonadotrophin-releasing hormone (GnRH) analogue buserelin (5 µg per animal). The naloxone experiment was repeated at 2 days after foaling. Blood for the determination of LH and PRL was withdrawn at 15 min intervals for 240 min, and naloxone or saline was injected after 60 min. Naloxone induced significant (P<0·05) LH release on days 172, 226 and 283 of pregnancy but not on days 26, 76 and 320 and 2 days after foaling. Buserelin caused a significant (P<0·05) increase in plasma LH concentrations on days 172, 226, 282 and 320 of pregnancy. The experiments indicate that endogenous opioids are involved in the inhibition of LH release during the second half of pregnancy in equine species. The deactivation of opioid effects on LH release might be a prerequisite for the onset of ovarian activity postpartum. Plasma PRL concentrations increased significantly (P<0·05) after naloxone administration on days 226, 282 and 320 of pregnancy. The naloxone-induced PRL release was most pronounced towards term, indicating an increase in the naloxone-releasable pool and/or the absence of other PRL-release inhibitory mechanisms.

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“…Most of these reports deal with progesterone and its fluctuations throughout the oestrous cycle and pregnancy or with oestrogens and androstenedione (Nett, Holtan & Estergreen, 1973;Pattison, Chen, Kelly & Brandt, 1974;Noden, Oxender & Hafs, 1975), but there is no information about the levels of plasma testosterone in the mare. In the present study, therefore, simultaneous measurements of plasma testosterone and progesterone in mares were taken during the oestrous cycle.…”

Section: Introductionmentioning

confidence: 99%

Testosterone and progesterone in peripheral plasma during the oestrous cycle of the mare

Silberzahn¹,

Quincey²,

Rosier³

et al. 1978

Reproduction

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Plasma Estrogens in Pregnant and Postpartum Mares2

Cited by 87 publications

References 16 publications

Changes in oestrone sulphate concentrations in peripheral plasma of Pony mares associated with follicular growth, ovulation and early pregnancy

Changes in oestrone sulphate concentrations in peripheral plasma of Pony mares associated with follicular growth, ovulation and early pregnancy

Opioidergic inhibition of luteinising hormone and prolactin release changes during pregnancy in pony mares

Testosterone and progesterone in peripheral plasma during the oestrous cycle of the mare

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