IDENTIFICATION OF ENDOGENOUS 19-NORTESTOSTERONE IN PREGNANT EWES BY GAS-CHROMATOGRAPHY MASS-SPECTROMETRY

Considered as a xenobiotic for many years, 19-nortestosterone has been extensively studied, Analyses developed to control the illegal use of this steroid in meat-producing animals led researchers to demonstrate the endogenous presence of 19-nortestosterone in several species, In this paper, the natural occurrence of 19-nortestosterone in its alpha form (epinandrolone) in the urine of pregnant sheep was demonstrated u sing gas chromatography-mass spectrometry, This reference method allow ed 17 alpha-nandrolone to be detected and identified, and the absence of the beta epimer in the urine of pregnant sheep to be demonstrated, 17 alpha-Nandrolone was accurately determined at different stages of p regnancy, The analyses showed that epinandrolone, which was not detect able in the urine of non-pregnant sheep, was excreted in small amounts (leading to a < 0.5 ppb concentration) during the first 4 months of p regnancy, 17 alpha-Nandrolone concentrations then increased during the last month until parturition, The origin of this molecule was not det ermined.