Assessment of ovarian function in the African elephant (Loxodonta africana) by measurement of 5α-reduced progesterone metabolites in serum and urine
✍ Scribed by M. Heistermann; B. Trohorsch; J. K. Hodges
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 114 KB
- Volume
- 16
- Category
- Article
- ISSN
- 0733-3188
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✦ Synopsis
We have previously shown that 5α-pregnane-3,20-dione (5α-DHP), and 5α-pregnane-3-ol-20-one (5α-P-3-OH) are the major luteal and circulating progestins in the African elephant. Therefore, the aim of the present study was to determine 1) circulating levels and patterns of secretion of 5α-DHP in relation to progesterone (P4) throughout the ovarian cycle, 2) the presence and relative abundance of 5αreduced progestins in urine and 3) whether their measurement in urine would provide a non-invasive method for monitoring luteal function. Urine samples were collected weekly throughout a total of 13 ovarian cycles from 5 females. In addition, matched blood samples were collected during 6 cycles from 2 of the 5 animals. All hormone measurements were carried out by enzymeimmunoassay following extraction. Urine was hydrolyzed prior to extraction. Profiles of P4 and 5α-DHP in serum followed a similar cyclic pattern and both measurements were significantly correlated (r = 0.78-0.98, mean 0.89, P < 0.001). Concentrations of 5α-DHP were, however, 10-20-fold higher than those of P4. In addition, 5α-DHP measurements showed a more pronounced luteal phase increase than that of immunoreactive P4. HPLC co-chromatography confirmed the presence of large amounts of 5α-P-3-OH in urine as a single immunoreactive peak, whereas 5α-DHP was present in very low levels and measurable only as one of several immunoreactive substances. Measurements of urinary 5α-P-3-OH were significantly correlated to serum 5α-DHP measurements in each of the 6 cycles (r = 0.72-0.93, mean 0.81, P < 0.001), whereas correlation coefficients between urinary and serum 5α-DHP values were generally lower (r = 0.34-0.83, mean 0.69) and significant in only 4 of the 6 cycles. Accordingly, only urinary excretion of 5α-P-3-OH, but not of 5α-DHP, exhibited a clear cyclic pattern, with consistently low levels of 0.15-0.20 µg/mg Cr in the follicular phase and 10fold elevated levels (1.8-2.2 µg/mg Cr) in the luteal phase. Based on the inter-