Patterns of Urinary and Fecal Steroid Excretion during the Ovarian Cycle and Pregnancy in the African Elephant (Loxodonta africana)

Abstract

The aims of the present study were to (i) determine the relative abundance of the 5α-reduced progestins 5α-pregnane-3-ol-20-one (5α-P-3OH) and 5α-dihydroprogesterone (5α-DHP) and progesterone (P4) in African elephant feces and to establish improved fecal progestin assays for monitoring ovarian function; and (ii) describe longitudinal profiles of urinary and fecal progestin and estrogen metabolites during pregnancy. Matched urine and fecal samples were collected weekly from six adult females throughout 18 nonfertile cycles and two complete pregnancies (89 and 93 weeks duration). Fecal samples were lyophilized and extracted with 80% methanol in water and immunoreactive 5α-P-3OH, 5α-DHP, and P4 and (for pregnant females only) estrone (E1) and estradiol (E2) determined by enzyme immunoassay. Urine samples were hydrolyzed, ether-extracted, and assayed for 5α-P-3OH, E1, and E2. HPLC cochromatography of fecal extracts with various radioactive progestin tracers confirmed the presence of large amounts of both 5-reduced progestins (5α-P-3OH>5α-DHP) but not of P4. 5-Reduced progestins (but not P4) were excreted in a cyclic pattern and levels were significantly correlated with urinary 5α-P-3OH. Fecal 5α-P-3OH showed the more pronounced and consistent luteal-phase elevation and a better correspondence to urine with respect to timing of the luteal-phase rise. Fecal and urinary 5-reduced progestins increased gradually during early pregnancy to maximum values around week 40–45. Levels gradually declined during the second half of pregnancy, reaching baseline values 2 days before parturition. Urinary estrogens did not show any cyclic pattern during the preconception period and levels remained low during the first 30 weeks of gestation. Thereafter, there was a rapid 10- to 20-fold increase to maximum values at mid-pregnancy, followed by a gradual decline to birth. There was no mid-pregnancy elevation in fecal estrogens, but there was a modest increase in E1 during the second half of gestation.