Demonstration of 2-unsaturated C-19-steroids in the urine of female Asian elephants, Elephas maximus, and their dependence on ovarian activity

Air-borne volatile substances have been demonstrated to signal oestrus, ind uce ovulation and synchronize ovarian activity in different mammals. An oes trous-related pheromone of the female Asian elephant (Elephas maximus) is k nown to induct? behavioural responses in elephant bulls. Additional data re vealed that timing of oestrus in females with close social relationships te nds to be synchronized. Therefore, urine from female Asian elephants might be expected to contain luteal phase-dependent volatile substances, which ma y function as additional chemical signals in this species. The aim of the p resent study was to identify such compounds and to investigate their patter n of excretion throughout the ovarian cycle. Urine samples were collected t hree times a week during the follicular phase and one to three times a week during the luteal phase from five adult female Asian elephants from a tota l of 13 non-conception cycles and one conception cycle, including the first 72 weeks of pregnancy. A simple headspace solid-phase microextraction meth od has been developed for quantification of urinary volatile substances and analysis was performed by gas chromatography. The comparison of urine coll ected during the follicular and the luteal phase indicated the presence of two luteal phase-dependent substances. Mass spectrometry was used to identi fy one substance as 5 alpha -androst-2-en-17-one and a second substance as the corresponding alcoholic compound 5 alpha -androst-2-en-17 beta -ol. The 5 alpha -androst-2-en-17 beta -ol and -17-one profiles reflected cyclic ov arian activity with clear (10-20-fold) luteal phase increases. Furthermore, measurements of both compounds were correlated positively with the concent ration of urinary pregnanetriol and indicated cycle duration (15.1 +/- 1.2 weeks) similar to that obtained from pregnanetriol measurements (15.2 +/- 1 .6 weeks). The results demonstrate the presence of two luteal phase-specifi c steroidal volatile compounds in elephant urine. One of the substances, 5 alpha -androst-2-en-17-one, has been demonstrated in human axillary bacteri al isolates. The measurement of both volatile substances in elephant urine can be used for rapid detection of the stage of the ovarian cycle, as the a nalysis can be completed within 2 h.