Evaluation of progesterone and 20-oxo-progestagens in the plasma of Asian (Elephas maximus) and African (Loxodonta africana) elephants

The corpus luteum of African elephants produces high amounts of 5α-reduced progesterone metabolites (5α-pregnane-3,20-dione and 5-α-pregnane-3α-ol-20-one), whereas progesterone itself is quantitatively less important, and plasma levels of progesterone during the estrous cycle in elephants are considerably lower than those of other mammals. The objective of this study was to compare the concentration of progesterone in plasma of Asian and African elephants as determined by specific progesterone assays with those of total immunoreactive progestagens containing a 20-oxo-group (20-oxo-P). These metabolites were determined by an enzyme immunoassay using an antibody against 5-α-pregnane-3β-ol-20-one, 3HS:BSA. Plasma of non-pregnant Asian (n = 4) and African (n = 4) elephants was collected at weekly intervals for periods of 8–15 months and at random intervals during pregnancy in one Asian elephant. High-performance liquid chromatography separation of plasma samples of both species demonstrated that in the 20-oxo-P assay, 5α-pregnane-3,20-dione makes up ˜60% of the total immunoreactive material. The progesterone and 20-oxo-P values during the estrous cycle showed a parallel pattern and were significantly correlated (P < 0.001; Asian: r = 0.80; y = 3.76 × –0.10; African: r = 0.75; y = 2.66 × –0.08). Progesterone and 20-oxo-P values in Asian and African elephants were <0.15 ng/ml during the follicular phase (weeks –4 to 0) of the estrous cycle; progesterone values during the luteal phase (weeks 2–9) were 0.60 ± 0.03 and 0.53 ± 0.03 ng/ml, and the 20-oxo-P values were 2.19 ± 0.16 and 1.48 ± 0.12 ng/ml, respectively. The 20-oxo-P values of the pregnant animal, although slightly higher, were comparable to those of non-pregnant elephants during the luteal phase. Total immunoreactive 20-oxo-P values are about three times higher than those of progesterone during the luteal phase, and 5α-pregnane-3,20-dione is the major immunoreactive 20-oxo-P in the plasma of Asian and African elephants. Zoo Biol 16:403–413, 1997. © 1997 Wiley-Liss, Inc.     

Fecal steroid metabolites and reproductive monitoring in a female Tsushima leopard cat (Prionailurus bengalensis euptilurus)

Although the Tsushima leopard cat (Prionailurus bengalensis euptilurus) is one of the most endangered mammals in Japan, its reproductive physiology and endocrinology have been not elucidated. The objective was to establish the non-invasive monitoring of reproductive endocrinology in a female Tsushima leopard cat and to identify the types of fecal reproductive steroid metabolites in this species. Fecal concentrations of estrogen and progestin were determined by enzyme immunoassays, from 60 d before to 60 d after the last copulation, during three pregnancies. Fecal estrogen metabolite concentrations were increased before/around the mating period and after mid-pregnancy. Fecal progestin metabolite concentrations increased after the last copulation and remained high during pregnancy. The gestation period was 65.0 ± 0.6 d (mean ± SD). Fecal extracts were separated by high-performance liquid chromatography for identification of fecal metabolites. Fecal estrogens were identified as estradiol-17β and estrone. Fecal progestins during pregnancy contained 5α-reduced pregnanes: 5α-pregnan-3α-ol-20-one, 5α-pregnan-3β-ol-20-one and 5α-pregnan-3,20-dione, and nonmetabolized progesterone was barely detected in feces. In conclusion, measurement of fecal estrogen and progestin metabolites was effective for noninvasive reproductive monitoring in the Tsushima leopard cat. An immunoassay for fecal estradiol-17β concentrations seemed useful to monitor follicular activity, whereas an immunoassay with high cross reactivity for 5α-reduced pregnanes was useful to monitor ovarian luteal activity and pregnancy.     

Use of group-specific antibodies to detect fecal progesterone metabolites during the estrous cycle of cows

Progesterone is metabolized to pregnanediones and hydroxylated pregnanes prior to its fecal excretion. Therefore, use of progesterone antibodies underestimates the actual amount of fecal metabolites. To improve the methodology of noninvasive fecal progesterone metabolite analysis, enzymeimmunoassays (EIA) using group-specific antibodies against 5-reduced 20-oxo-pregnane-C3-conjugates were developed. Fecal and milk samples were collected at 1- to 2-d intervals during the morning and evening milking throughout 1 estrous cycle in dairy cows (n = 12). Six immunoreactive metabolites were detected in the feces with high performance liquid chromatography (HPLC), eluting as 5α- and 5β-reduced pregnanes containing a 20-oxo-group (20-oxo-pregnanes). Fecal samples of 3 cows were analyzed by 3 EIAs using antibodies against 4-pregnene-6α-ol-3,20-dione 6HS:BSA (6HS-progesterone), 5α-pregnane-3β-ol-20-one 3HS:BSA and 5β-pregnane-3β-ol-20-one 3HS:BSA, respectively. The follicular and luteal phases were identifiable with each EIA. Luteal phase values and the differences between mean follicular (Days 0 to 2 and 19 to 21) and luteal phase (Days 10 to 16) values obtained with the 5-pregnane EIAs were 3- to 4-fold higher than with the 6HS-progesterone EIA. Since results with the former 2 EIAs were almost identical, the remaining samples were only analyzed by the EIA for 5β-pregnane-3α-ol-20-one. Fecal 20-oxo-pregnane concentrations were parallel to milk progesterone values, but had a lag time of about 0.5 d; the coefficient of correlation (P < 0.001) was 0.76 (y = 155.2 × + 37.2). Fecal 20-oxo-pregnane concentrations during the follicular and luteal phase were 39.5 ± 2.2 and 341 ± 15.2 ng/g feces, respectively. In conclusion, fecal 20-oxo-pregnanes are significantly correlated to milk progesterone concentrations. They consist of several metabolites and compared to a 6HS-progesterone antibody, their evaluation was improved using antibodies against 5-reduced pregnanes.     

The impact of ecological variability on the reproductive endocrinology of wild female African elephants

Non-invasive endocrine methods enable investigation of the relationship between ecological variation and ovarian activity and how this impacts on demographic processes. The underlying physiological factors driving high variation in inter-calving intervals among multi-parous African elephants offer an interesting system for such an investigation. This study investigates the relationship between Normalized Differential Vegetation Index (NDVI), an ecosystem surrogate measure of primary productivity, and fecal progestin concentrations among wild female elephants. Matched fecal samples and behavioral data on reproductive activity were collected from 37 focal individuals during the two-year study. Linear mixed models were used to explore the relationship between fecal 5alpha-pregnane-3-ol-20-one concentrations and the independent variables of NDVI, calf sex, female age, gestation day, and time since last parturition. Among both non-pregnant and pregnant females, fecal 5alpha-pregnane-3-ol-20-one concentrations were significantly correlated with time-specific NDVI indicating a strong relationship between ecological conditions and endocrine activity regulating reproduction. In addition, the age of a female and time since her last parturition impacted hormone concentrations. These results indicate that the identification of an individual's reproductive status from a single hormone sample is possible, but difficult to achieve in practice since numerous independent factors, particularly season, impact fecal hormone concentrations. Regardless of season, however, fecal 5alpha-pregnane-3-ol-20-one concentrations below 1 microg/g were exclusively collected from non-pregnant females, which could be used as a threshold value to identify non-pregnant individuals. Collectively the information generated contributes to a better understanding of environmental regulation of reproductive endocrinology in wild elephant populations, information salient to the management and manipulation of population dynamics in this species.     

Ovarian function in the elephant: luteinizing hormone and progesterone cycles in African and Asian elephants

Serum samples were collected weekly for 3 yr from two female African elephants, for 18 mo from two other female African elephants, and for 2 yr from two female Asian elephants. Animals were not sedated at the time of blood collection. Ovarian cycles, characterized by changes in progesterone and immunoreactive luteinizing hormone (ILH) concentrations, averaged 15.9 +/- 0.6 wk (N = 25) for African females and 14.7 +/- 0.5 wk for Asian females (N = 10). The length of the active luteal phase averaged 10.0 +/- 0.3 wk for African elephants (range 8-14 wk) and 10.6 +/- 0.6 wk for Asian females (range 9-13 wk). Interluteal phases were 5.9 +/- 0.6 wk for African females and 4.2 +/- 0.5 wk for Asian females. One African female (Maliaca) had two extended interluteal phases, both occurring between the months of February and May. Excluding these two periods, there were no differences in the length of the ovarian cycle or the length of the luteal phase between species of elephant. Serum progesterone in both species ranged from less than 50 pg/ml to 933 pg/ml. Average progesterone concentrations during the luteal phase were significantly lower in African elephants compared with Asian elephants (328 +/- 13, N = 30 cycles vs. 456 +/- 23, N = 14 cycles; p less than 0.001). ILH ranged from nondetectable to 11.6 ng/ml. These data suggest that the length of the ovarian cycle in the African elephant is about 16 wk and confirm that the length of the ovarian cycle in the Asian elephant is about 15 wk.     

Non-invasive assessment of the reproductive cycle in free-ranging female African elephants (Loxodonta africana) treated with a gonadotropin-releasing hormone (GnRH) vaccine for inducing anoestrus

ABSTRACT: BACKGROUND: In southern Africa, various options to manage elephant populations are being considered. Immunocontraception is considered to be the most ethically acceptable and logistically feasible method for control of smaller and confined populations. In this regard, the use of gonadotropin-releasing hormone (GnRH) vaccine has not been investigated in female elephants, although it has been reported to be safe and effective in several domestic and wildlife species. The aims of this study were to monitor the oestrous cycles of free-ranging African elephant cows using faecal progestagen metabolites and to evaluate the efficacy of a GnRH vaccine to induce anoestrus in treated cows. METHODS: Between May 2009 - June 2010, luteal activity of 12 elephant cows was monitored non-invasively using an enzyme immunoassay detecting faecal 5alpha-reduced pregnanes (faecal progestagen metabolites, FPM) on a private game reserve in South Africa. No bulls of breeding age were present on the reserve prior to and for the duration of the study. After a 3-month control period, 8 randomly-selected females were treated twice with 600 micrograms of GnRH vaccine (Improvac[REGISTERED SIGN], Pfizer Animal Health, Sandton, South Africa) 5-7 weeks apart. Four of these females had been treated previously with the porcine zona pellucida (pZP) vaccine for four years (2004-2007). RESULTS: All 12 monitored females (8 treated and 4 controls) showed signs of luteal activity as evidenced by FPM concentrations exceeding individual baseline values more than once. A total of 16 oestrous cycles could be identified in 8 cows with four of these within the 13 to 17 weeks range previously reported for captive African elephants. According to the FPM concentrations the GnRH vaccine was unable to induce anoestrus in the treated cows. Overall FPM levels in samples collected during the wet season (mean 4.03 micrograms/gram dry faeces) were significantly higher (P<0.002) than the dry season (mean 2.59 micrograms/gram dry faeces). CONCLUSIONS: The GnRH vaccination protocol failed to induce anoestrus in the treated female elephants. These results indicate that irregular oestrous cycles occur amongst free-ranging elephants and are not restricted to elephants in captivity. The relationship between ecological conditions and endocrine activity were confirmed. Free-ranging female elephants were observed to not cycle continuously throughout the year in the absence of adult bulls.     

Metabolism of progesterone by Dioscorea deltoidea suspension cultures

Dioscorea deltoidea plant tissue suspension cultures are capable of metabolizing progesterone to 5α-pregnan-3-β-ol-20-one and 5α-pregnan-3β,20β-diol. The latter product has not previously been reported as a metabolic product of progesterone by plant systems. Both transformation products are present as conjugates in this plant tissue culture.     

Biotransformation of progesterone by suspension cultures of Digitalis purpurea cultured cells

It has been shown that the cultured cells of Digitalis purpruea are capable of transforming progesterone (I) to 5α-pregnane-3,20-dione (II), 5α-pregnan-3β-ol-20-one (III), its glucoside (IV), 5α-pregnane-3β,20α-diol (V), its glucoside (VI), 5α-pregnane-3β,20β-diol (VII), its glucoside (VIII), Δ⁴-pregnen-20α-ol-3-one (IX), its glucoside (X), Δ-pregnen-20β-ol-3-one (XI) and its glucoside (XII). 5α-Pregnan-3β-ol-20-one glucoside (IV), 5α-pregnane-3β,20α-diol glucoside (VI), 5α-pregnane-3β,20β-diol glucoside (VIII), Δ⁴-pregnen-20α-ol-3-one glucoside (X) and Δ⁴-pregnen-20β-ol-3-one glucoside (XII) have been found for the first time as new metabolises by plant tissue cultures. A scheme for the biotransformation of progesterone (I) has been proposed, and the reduction and glucosidation activities distinctly have been observed in these cultured cells.     

Secretory Pattern of Inhibin During Estrous Cycle and Pregnancy in African (Loxodonta africana) and Asian (Elephas maximus) Elephants

The ovary of female elephants has multiple corpora lutea (CL) during the estrous cycle and gestation. The previous reports clearly demonstrated that inhibin was secreted from lutein cells as well as granulosa cells of antral follicles in cyclic Asian elephants. The aim of this study is to investigate the inhibin secretion during the pregnancy in African and Asian elephants. Two African elephants and two Asian elephants were subjected to this study. Circulating levels of immunoreactive (ir‐) inhibin and progesterone were measured by radioimmunoassay. Four pregnant periods of an African elephant and three pregnant periods of an Asian elephant were analyzed in this study. Circulating levels of ir‐inhibin started to increase at 1 or 2 week before the ovulation and reached the peak level 3 or 4 weeks earlier than progesterone during the estrous cycle in both African and Asian elephants. After last luteal phase, the serum levels of ir‐inhibin remained low throughout pregnancy in both an African and an Asian elephant. The mean levels of ir‐inhibin during the pregnancy were lower than the luteal phase in the estrous cycle despite high progesterone levels were maintained throughout the pregnancy. These results strongly suggest that CL secrete a large amount of progesterone but not inhibin during the pregnancy in elephants. Zoo Biol 31:511‐522, 2012. © 2011 Wiley Periodicals, Inc.     

Contraceptive potential of the porcine zona pellucida vaccine in the African elephant (Loxodonta africana)

Immunocontraception has been successful in controlling free-roaming equids; however, what is the potential for the immunocontraceptive control of the African elephant (Loxodonta africana)? The porcine zona pellucida (pZP) glycoproteins share antigenic domains with the African elephant zona pellucida (elZP) glycoproteins, and anti-zona pellucida serum antibodies have been successfully stimulated. To determine the cross-reactivity of the pZP and elZP, immunocytochemistry was evaluated by light and electron microscopy. Specifically, the binding of polyclonal antibodies against total heat-solubilized-porcine zona pellucida to fixed elephant ovary sections was evaluated. The elZP of primary, secondary and tertiary follicles was recognized by the rabbit-anti-pZP serum, but there was no apparent recognition of the primordial follicles. The ability of anti-pZP antibodies to recognize the elZP demonstrates that there is molecular homology between the pZP and elZP glycoproteins. This homology makes the African elephant a candidate for pZP immunocontraception. Three captive elephants were vaccinated with 400 micrograms pZP with a synthetic trehalose dicorynomycolate (S-TDCM) adjuvant. The elephants received 2 boosters of 600 micrograms pZP at 4 wk and 10 m.o. after the primary vaccination. The vaccinated female elephants developed significant (P < 0.05) titers to pZP over prevaccination levels. These levels persisted for 12 to 14 m.o. after the third vaccination. This preliminary evidence shows that the female elephant can develop significant serum antibody levels to pZP. These levels of antibodies are comparable to those required in horses for successful immunocontraception. Thus, porcine zona pellucida immunocontraception might be used to control elephant populations.     

Detection and identification of plasma progesterone metabolites in the female Florida manatee (Trichechus manatus latirostris) using GC/MS/MS

Florida manatees (Trichechus manatus latirostris) have relatively low peripheral concentrations of progesterone (P4). The objective of this study was to determine if these relatively low P4 concentrations are associated with a high ratio of progestin metabolites and to document metabolite concentrations from individual blood samples obtained from manatees during diestrus or pregnancy. Metabolites known to exist in elephants—terrestrial manatee relatives—were targeted. These included 5α-reduced progestins (5α-pregnane-3,20-dione [5α-DHP] and 3α-hydroxy-5α-pregnan-20-one [5α-P3-OH]) and 17α-hydroxyprogesterone (17α-OHP), which occurs in Asian elephants. An additional, inactive metabolite, 20α-hydroxyprogesterone (20α-OHP), indicative of P4 overproduction, was also targeted. Progesterone itself was the predominant progestin detected in pregnant and nonpregnant manatee plasma (n = 10) using gas chromatography-mass spectrometry with tandem quadrupole detectors (GC/MS/MS). Progesterone concentrations in pregnant females varied from early (moderate to high) through mid and late (low) pregnancy. Progesterone concentrations ranged from low to high in nonpregnant, nonlactating females. The most commonly detected metabolite was 5α-P3-OH (n = 7), which occurred in pregnant (lower limit of detection [LLOD] to high) and nonpregnant (trace to high) females. The 5α-DHP metabolite was also detected in pregnant (LLOD to moderate) and nonpregnant (low) females. The 17α-OHP metabolite was not detected in any tested female. The 20α-OHP metabolite was detected in one nonpregnant, nonlactating, captive female (LLOD). Metabolites were most prevalent during early pregnancy, concurrent with maximum P4 concentrations. Based on their concentrations in peripheral circulation, we inferred that these metabolites may have, opposite to elephants, a limited physiologic role during luteal, pregnant, and nonpregnant phases in the manatee.     

Measurement of fecal steroids in the black rhinoceros (Diceros bicornis) using group-specific enzyme immunoassays for 20-oxo-pregnanes

The metabolism and excretion of progesterone in different animal species results in several fecal 5-reduced progesterone metabolites (pregnanes), which in recent studies were quantified using progesterone antibodies. To increase the accuracy of fecal 20-oxo-pregnane evaluations in the black rhinoceros, enzyme immunoassays (EIA) using antibodies against 5α-pregnane-3β-ol-20-one 3HS:BSA (5α-20-one EIA) and 5β-pregnane-3α-ol-20-one 3HS:BSA (5β-20-one EIA) were developed. The assays showed high crossreactivities with pregnanes containing a 20-oxo group and are referred to as group-specific; results of these assays were compared with an EIA using an antibody against 6HS-progesterone (4-ene-20-one EIA). Fecal samples of both subspecies of the black rhinoceros (Diceros bicornis michaeli, n = 5, and Diceros bicornis minor, n = 1) during pregnancy were collected 1–3 times/week. HPLC separation showed three major immunoreactive fecal 20-oxo-pregnane peaks; their elution profiles and different crossreactivities in the three EIAs provided strong evidence that these peaks are 5α-pregnane-3, 20-dione, 5α-pregnane-3α-ol-20-one, and 5α-pregnane-3β-ol-20-one. Pregnane values in the pregnant animals continuously increased between months 3–7 and were significantly (P < 0.01) elevated above the levels of nonpregnant animals (0.2 μg/g) by week 11. During months 6–13 concentrations in the 5α-20-one and in the 5β-20-one EIA (5–11 μg/g) were significantly (P < 0.01) higher than in the 4-ene-20-one EIA (1.5–3 μg/g). In conclusion, the immunoreactive fecal 20-oxo-pregnane metabolites in the black rhinoceros are determined more accurately with antibodies against pregnane-20-one-C3 conjugates, as compared with a progesterone antibody. © 1996 Wiley-Liss, Inc.     

The effects of progesterone and its metabolites on the induction of sexual receptivity in rats

Estrogen-primed female rats were administered progesterone, 5 a-pregnan-3,20-dione, 5a-pregnan-3a-ol-20-one, 5a-pregnan-3β-ol-20-one, 4-pregnen-20a-ol-3-one, and 5a-pregnan-20a-ol-3-one in oil or oil alone and tested for the display of lordosis behavior 3 and 5 hr after progestin treatment. Progesterone was the most effective progestin in facilitating lordosis behavior. 5a-Pregnan- 3,20-dione and 5a-pregnan-3a-ol-20-one were partially effective, while the other progestins were no more effective than oil. The data suggest that the neuronal system which controls lordosis behavior is not entirely specific for progesterone.     

Assessment of ovarian function in the African elephant (Loxodonta africana) by measurement of 5α-reduced progesterone metabolites in serum and urine

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.     

Concentrations of progesterone,testosterone and estradiol-17β in the serum during the estrous cycle of Asian elephants (Elephas maximus)

The levels of progesterone, testosterone and estradiol-17β in serum samples from two female Asian elephants were measured for the period of 32 months from February 1987 to September 1989. Serum samples were collected weekly from unanesthetized elephants. Each elephant showed eight ovarian cycles in 32 months. Ovarian cycles, characterized by changes in concentrations of serum progesterone, averaged 16.8 ± 0.6 (mean ± SEM. n = 14) weeks in length. The changes in concentrations of testosterone in the serum showed a similar pattern to those of progesterone with a striking increase noted during the luteal phase. The highest levels of serum estradiol-17β were noted when progesterone levels showed low basal values. These results suggest that estradiol-17β may be an index of follicular maturation during the estrous cycle in Asian elephants, and that the ovaries of Asian elephants may produce testosterone in the luteal phase.     

Reproductive cycle of the elephant

The combination of a few factors, including poor captive reproduction, secession of importation from the wild and advances in hormone detection and ultrasonography, has contributed to the current knowledge on the elephant reproductive cycle. Several reproductive features in elephants differ markedly from other mammals. These include the urogenital tract anatomy, length and structure of the reproductive cycle, the formation of multiple corpora lutea and the type and secretion pattern of reproductive hormones. Being 13-18 weeks in length, the elephant estrous cycle is the longest amongst all studied non-seasonal mammals to date. Progesterone increases 1-3 days after ovulation, indicating the start of the luteal phase, which lasts 6-12 weeks. This is followed by a 4- to 6-week follicular phase that is concluded by two, precisely spaced and timed, LH surges. In general, the first, anovulatory LH surge occurs exactly 19-21 days before the second, ovulatory surge. Normally, a single follicle is ovulated. However, beside a corpus luteum (CL) forming on the site of ovulation, multiple accessory CLs can be found on the ovaries. Unlike many other species, the predominant progestagen secreted by luteal tissues is not progesterone, but rather its 5-alpha-reduced metabolites. The currently known aspects of the unique estrous cycle in Asian and African elephants, covering estrous behavior, circulating hormones, ultrasonography and anatomy of the reproductive organs as well as hormonal manipulation treatment possibilities, will be reviewed here.     

Stereospecific reduction of progesterone by Pisum sativum

[4 -¹⁴C]-Progesterone was applied to the leaves of growing pea plants, Pisum sativum. After 3 weeks, about 50% of the administered steroid was reduced, about 20% being reduced to 5α-pregnane-3α,20β-diol as the major metabolite. The radioactivities of 5α-pregnane-3α,20α-diol and 5α-pregnane-3α,20β-diol after 3 weeks were more than twice those after one week. The following radioactive metabolises were also isolated: 5α-pregnane-3,20-dione; 20α-hydroxy-4- pregnen-3-one; 20β-hydroxy-4-pregnen-3-one; 3α-hydroxy-5α-pregnan-20-one; 3α-hydroxy-5β-pregnan-20-one; 3β-hydroxy- 5α-pregnan-20-one; 20β-hydroxy-5α-pregnan-3-one; 5α-pregnane-3β,20β-diol; and 5β-pregnane-3α,20β-diol. The radioactivities of the 5α-pregnane derivatives were considerably higher than those of the corresponding 5β-pregnane derivatives.     

The use of low-frequency vocalizations in African elephant(Loxodonta africana) reproductive strategies

Fertility-advertisement calls in females are predicted to occur in nonmonogamous species where males and females are widely separated in space. In African elephants, low-frequency vocalizations have thus been suggested as a reproductive strategy used by fertile females to attract mates. This study examined the use of low-frequency vocalizations with respect to different phases of the estrous cycle in African elephants by simultaneously monitoring vocalizations, behavior, and hormonal profiles. Subjects were one male and six female African elephants housed at Disney's Animal Kingdom. No acoustically distinct vocalizations were restricted to the ovulatory follicular phase. However, overall rate of low-frequency vocalization as well as the rate of one acoustically distinct vocalization changed over the estrous cycle, with highest rates of calling related to the first period of follicular growth, or anovulatory follicular phase. Elevated rates of vocalization thus were not restricted to behavioral estrus and occurred much earlier in the estrous cycle than in most species that produce fertility-advertisement calls. Both herd composition and elephant identity also affected rates of vocalization. Vocalizations therefore may not be reliable signals of actual fertility. However, the increase in vocalizations in advance of estrus may attract males to the herd prior to ovulation, facilitating both male-male competition and female choice. Once present in the herd, males may then switch strategies to use more reliable chemical and visual cues to detect ovulating females.     

Metabolism of progesterone by chorionic cells of the early sheep conceptus invitro

Progesterone-4-¹⁴C was extensively metabolized during incubation with dispersed trophoblast prepared from chorionic membranes of the 21-day sheep conceptus. Of the metabolites formed, 17,20α-dihydroxypregn-4-en-3-one, 20α-hydroxypregn-4-en-3-one, 20(β-hydroxypregn-4-en-3-one, 5α-pregnane-3α,17,20α-triol, 5β-pregnane-3ga, 17,20α-triol, 5β-pregnane-3g,20α-diol, 3β-hydroxy-5α-pregnan-20-one, 3α-hydroxy-5β-pregnan-20-one, 20β-hydroxy-5β-pregnan-3-one, 5α-pregnane-3,20-dione and 5β-pregnane-3,20-dione were identified. These findings indicate that the sheep conceptus acquires extensive steroid metabolizing capability very early in pregnancy.     

Secretory patterns of serum prolactin in Asian (Elephas maximus) and African (Loxodonta africana) elephants during different reproductive states: Comparison with concentrations in a noncycling African elephant

Serum prolactin was quantified in adult female Asian (Elephas maximus) and African (Loxodonta africana) elephants during various reproductive states and the profiles compared to that in a noncycling African elephant. In reproductively normal elephants, there was no effect of season, estrous cycle stage, or lactational status on quantitative or qualitative prolactin secretion (P > 0.05), nor where there any differences (P > 0.05) in overall prolactin concentrations between species. In pregnant elephants, prolactin concentrations remained at baseline for the first 4–6 months of gestation. Thereafter, concentrations during early pregnancy averaged ∼four-fold higher than those during the estrous cycle, increasing to ∼100-fold over baseline during mid- to late gestation in both species. In contrast to cycling elephants, prolactin concentrations in an African elephant exhibiting chronic anovulation (on the basis of an acyclic serum progesterone profile) and mild galactorrhea were consistently about five-fold higher (P < 0.05), suggesting she is hyperprolactinemic. Other endocrinological assesments confirmed the hypogonadal state of this female. Serum estradiol concentrations were consistently at or below detectable levels. Additionally, no preovulatory luteinizing hormone (LH) surges occurred in daily serum samples analyzed over a 12-month period. The pituitary was not totally refractory, however, and responded with a several-fold increase in serum LH concentration (peak, 3.07 ng/ml) over baseline (0.75 ng/ml) after i.v. injection of gonadotropin-releasing hormone. This study describes normal baseline serum prolactin values for Asian and African elephants and is the first to identify hyperprolactinemia as a possible cause of reproductive acyclicity and galactorrhea in an African elephant. Zoo Biol 16:149–159, 1997. © 1997 Wiley-Liss, Inc.