Biliary elimination of endogenous nortestosterone by pregnant cows

A temporal study of the biliary elimination of endogenous 19-nortestosteron e during two successive pregnancies was made in three co-ws with cannulated gall bladders. Rile samples were analysed for 17 beta-19-nortestosterone ( beta-NT) and the 17 alpha-epimer (alpha-NT) by using high resolution gas ch romatography and mass spectroscopy. No beta-NT was detected in any of the s amples analysed. However, alpha-NT was detected from around 120 days of ges tation in each of the cows. Peak concentrations were observed in the last w eek before calving and ranged from 9.5 to 36.7 ng/ml, After parturition, th e concentrations of alpha-NT declined rapidly and mere undetectable by seve n days after calving, and it was not defected again until after 120 days of gestation. The biliary concentrations of alpha-NT defected subsequently we re: similar to those observed in cattle several weeks after an exogenous in jection of the synthetic ester beta-NT phenylpropionate.