Horse plasma corticotrophin-releasing hormone (CRH): characterisation and lack of a late gestational rise or a plasma CRH-binding protein

in Journal of Endocrinology
Authors:
M J Ellis
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J H Livesey
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R A Donald
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Abstract

Immunoreactive corticotrophin-releasing hormone (irCRH) was present in methanolic extracts of equine peripheral blood and showed no elevation in maternal peripheral serum in late gestation (0·54 ±0·25 pmol/l; mean ± s.d.) compared with control horses (0·41 ± 015 pmol/l). The irCRH of methanolic extracts of pituitary venous plasma had a similar elution position following reverse-phase HPLC to synthetic human CRH(1–41) and to irCRH released from horse stalk-median eminence tissue incubated in vitro. Gel chromatographic studies showed no evidence for a plasma CRH-binding protein (CRHBP) analogous to that found in human plasma in either peripheral blood from normal or pregnant horses or in pituitary venous plasma sampled from a cannulated horse. CRH-binding activity was detectable in peripheral plasma from one horse, however the molecular size of this was indicative of a γ-globulin rather than the 37 kDa CRHBP.

These studies suggest that, unlike in the human, CRH does not rise to high values in late gestation nor circulate in a bound form in equine plasma.

Journal of Endocrinology (1994) 143, 455–460

 

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