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Assessment of ovarian function in the African elephant ( Loxodonta africana ) by measurement of 5α‐reduced progesterone metabolites in serum and urine
Author(s) -
Heistermann M.,
Trohorsch B.,
Hodges J. K.
Publication year - 1997
Publication title -
zoo biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.5
H-Index - 54
eISSN - 1098-2361
pISSN - 0733-3188
DOI - 10.1002/(sici)1098-2361(1997)16:3<273::aid-zoo7>3.0.co;2-7
Subject(s) - luteal phase , urine , endocrinology , biology , medicine , estrous cycle , urinary system , ovary , hormone
We have previously shown that 5α‐pregnane‐3,20‐dione (5αDHP), 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 5α‐reduced 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 measurement, 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. I 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 0.15–0.20 μ/mg Cr in the follicular phase and 10‐fold elevated levels (1.8–2.2 μg/mg Cr) in the luteal phase. Based on the intervals between successive luteal phase increases in urinary 5α‐P‐3‐OH, a mean cycle length of 14.1 ± 1.8 weeks, comprising a follicular phase of 5.0 ± 0.9 weeks and a luteal phase of 9.1 ± 1.4 weeks was determined for the 13 cycles studied. The results indicate that measurements of 5α‐P‐3‐OH in urine provide a reliable non‐invasive method for monitoring luteal function in the African elephant. Zoo Biol 16:273–284, 1997. © 1997 Wiley‐Liss, Inc.