Urinary steroid evaluations to monitor ovarian function in exotic ungulates: IV. Estrogen metabolism in the okapi (Okapia johnstoni)

Abstract

In this investigation, an attempt was made to identify the major urinary estrogen metabolites in the okapi by radioisotope infusion and by chromatographic separation procedures. The results suggest that the urinary estrogens are excreted in concentrations below the limit of sensitivity of conventional assay systems. In addition, a variety of contaminants with estrogenic immunoreactivity are present in okapi urine that are not necessarily correlated with follicular activity. A great proportion of circulating estrogen is eliminated in fecal material. However, the rate of elimination is slow, and the extraction procedures necessary to detect the metabolites are tedious, which would prevent the practical application of this procedure for monitoring follicular activity.

Excretion and metabolic fate of radiolabeled estradiol and testosterone in the cockatiel (Nymphicus hollandicus)

“…Although fecal monitoring has been used in other avian species to measure daily changes in sex steroid production [Bishop and Hall, 1991;Yamaguchi and Ishii, 1991;Cockrem and Rounce, 1994;Lee et al, 1995], the present data are the first to demonstrate that daily fecal/urine measurements reflect primarily the excretion products of estradiol and testosterone produced during the previous 24 hr. These results are unlike mammalian studies in which radiolabeled steroid excretion has been relatively slow and overall recovery has been low [Shille et al, 1984;Loskutoff et al, 1987;Ziegler et al, 1989;Hindle and Hodges, 1990;Czekala et al, 1992;Shideler et al, 1993]. The present report reveals a recovery of 75% of each radiolabeled steroid administered within 24 hr after radiolabel injection.…”

Excretion Patterns of Fecal Progestagens, Androgen and Estrogens During Pregnancy, Parturition and Postpartum in Okapi (Okapia johnstoni)

“…Pregnancy in okapi could not be diagnosed using our assay of fecal iE 2 and iE 1 . It has been reported that a variety of contaminants with estrogenic immunoreactivity are present in okapi urine [10]. When assaying fecal estrogens, a pretreatment such as purification of fecal steroid extracts may be required.…”

“…However, the day of their peak could not be identified since fecal samples were not collected on the day of parturition and the 2nd and 3rd days postpartum. Given the report that tritiated E 2 infused via the jugular vein was detected in feces at 72 h post-injection [10], circulating estrogens probably take 3 days to be excreted in feces. It seems that the circulating levels of estrogens reached a peak within the period from 3 days prepartum to the day of parturition.…”

“…Endocrinological observations on reproductive physiology in female okapi have mainly been reported by the groups of Loskutoff [10][11][12][13] and Schwarzenberger [14][15][16][17]. Both groups have attempted to monitor luteal activity and diagnose pregnancy by assays of hormone metabolites in excreta.…”

“…Urinary levels of estrogens have been reported to increase sharply 1-2 days after complete luteal regression [12]. A peak consistent with estradiol-17β (E 2 ) elution patterns has also been observed by high performance liquid chromatography in okapi urine collected during estrus [10]. However, the excretion patterns of fecal estrogens have not been clarified.…”