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Biliary elimination of endogenous nortestosterone by pregnant cows
  1. J. D. G. McEvoy, MVB, PhD, MRCVS1,
  2. C. E. McVeigh, ONC1,
  3. W. J. McCaughey, MA, MSc, MVB, PhD, MRCVS1 and
  4. S. A. Hewitt, BSc, PhD1
  1. 1 Residues Department, Departnent of Agriculture for Northern Ireland, Veterinary Sciences Division, Stoney Road, Stormont, Belfast BT4 3SD

Abstract

A temporal study of the biliary elimination of endogenous 19-nortestosterone during two successive pregnancies was made in three cows with cannulated gall bladders. Bile samples were analysed for 17β-19-nortestosterone (β-NT) and the 17α-epimer (α-NT) by using high resolution gas chromatography and mass spectroscopy. No β-NT was detected in any of the samples analysed. However, α-NT was detected from around 120 days of gestation in each of the cows. Peak concentrations were observed in the last week before calving and ranged from 9.5 to 36.7 ng/ml. After parturition, the concentrations of α-NT declined rapidly and were undetectable by seven days after calving, and it was not detected again until after 120 days of gestation. The biliary concentrations of α-NT detected subsequently were similar to those observed in cattle several weeks after an exogenous injection of the synthetic ester β-NT phenylpropionate.

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