Non-invasive monitoring of ovarian function in Asian elephants (Elephas maximus) by measurement of urinary 5β-pregnanetriol

Abstract

The development of an enzymeimmunoassay for 5β-pregnanetriol and its use for noninvasive monitoring of reproductive cycles in Asian elephants is described. Gas chromatography-mass spectrometry (GCMS) and high performance liquid chromatography (HPLC) confirmed the presence of 5β-pregnane-3α,17α,20α/β-triols as the two most abundant urinary progesterone metabolites. The assay developed used the antiserum anti-5β-pregnane-17α,20α-diol-3α-γ1 glucuronide but was designed to measure the free steroid in urine samples after hydrolysis and extraction. HPLC confirmed the presence of immunoreactive pregnanetriol in urine, but indicated that the measurement was nonspecific. Immunoreactive pregnanetriol concentrations were significantly correlated with the concentrations of both progesterone (r = 0.98, n = 269, P < 0.01) and 17α-hydroxyprogesterone (r = 0.95, n = 205, P < 0.01), the metabolic precursor of pregnanetriol. The mean ± SEM deviation of cycles as determined by measurements of plasma progesterone, 17α-hydroxyprogesterone and urinary pregnanetriol, respectively, were 15.54 ± 1.5 (n = 23, where n = number of cycles), 15.21 ± 1.7 (n = 15) and 15.45 ± 0.94 weeks (n = 20). These results demonstrate that it is possible to monitor ovarian function in Asian elephants by the measurement of urinary immunoreactive pregnanetriol concentrations.