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S. Atkinson, W. G. Gilmartin and B. L. Lasley

Adult male Hawaiian monk seals were administered a gonadotrophin-releasing hormone (GnRH) agonist to determine its effectiveness in reducing the testicular production of testosterone. Blood samples were collected from four treated seals and two control seals at weekly intervals for 10 weeks and again at the beginning of the following breeding season. The GnRH-agonist had an initial, brief, stimulating effect on circulating testosterone, but this was followed by an inhibitory effect that lasted for 7 to 8 weeks. The plasma concentrations of testosterone were within normal ranges by the following spring. These results demonstrate a reversible form of long-term androgen suppression, which may have applicability in a variety of wildlife management programmes.

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Kay Nakakura, Nancy M. Czekala, B. L. Lasley and K. Benirschke

Summary. Gonadal and adrenal steroid hormone levels in plasma were measured in pregnant, non-pregnant and fetal armadillos. Progesterone demonstrated the largest placental gradient with levels 6 to 10-fold higher in the fetus. Testosterone levels were higher in male and lower in female fetuses, when compared to the respective maternal serum values. Dehydroepiandrosterone, and cortisol were consistently high in maternal as compared to matched fetal serum samples whereas the reverse was true for androstenedione. Tissue incubations with labelled pregnenolone indicated the major source of progesterone production to be the fetal adrenal whereas the fetal testes demonstrated a major conversion product consistent with dehydroepiandrosterone.

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N. M. Czekala, J. F. Roser, R. B. Mortensen, T. Reichard and B. L. Lasley

Summary. Daily urine samples were collected from 4 adult female gorillas over 7 menstrual cycles. Urinary oestrone conjugate and pregnanediol-3-glucuronide (PDG) were measured by radioimmunoassay; LH was measured by enzyme immunoassay and each hormone was indexed by creatinine. The quantity of urinary LH during the ovulatory surge was positively correlated with the quantity of PDG excreted during the luteal phase (r = 0·87, P = 0·0013). The observations indicate a relationship between the quality of the LH surge and the levels of PDG in the luteal phase and suggest that both the LH surge and subsequent luteal phase function may be predictable from the oestrogen excretion profile during the follicular phase.

Keywords: gorilla; oestrogen; progesterone; LH; luteal function

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J. K. Hodges, B. A. Gulick, N. M. Czekala and B. L. Lasley

Summary. Changes in the excretion of immunoreactive oestrogens and biologically active LH were assessed from measurements on small samples of urine collected from a capuchin, a tamarin, a spider monkey and a squirrel monkey. The hormone profiles were used to time matings of the capuchin and spider monkey; conception and pregnancy ensued. Detailed analysis of one urine sample from each female by using partition chromatography and reverse-phase high-pressure liquid chromatography showed that oestrone was more abundant than oestradiol-17β and oestriol combined, but the relative contribution of individual oestrogens to the total oestrogen complement differed. In the sample from the capuchin, an immunoreactive oestrogen slightly less polar than oestradiol appeared to be the most abundant urinary oestrogen.

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Joyce H. Poole, L. H. Kasman, E. C. Ramsay and B. L. Lasley

Summary. Urine samples were obtained from free-ranging African elephants that were considered to be in and out of musth. Testosterone concentrations, measured by radioimmunoassay were significantly greater in males that were in or around the time of behavioural musth. This study supports a correlation between the observed behavioural characteristics of musth and urinary testosterone levels.

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Joan E. Sawyer-Steffan, B. L. Lasley, J. D. Hoff and S. S. C. Yen

Summary. The in-vitro test of rat interstitial cell testosterone secretion and a radioimmunoassay (RIA) were used to explore the nature of the LH released in women in response to LH-RH. The ratio of in-vitro bioactivity to immunoreactivity (B:I) calculated for serum samples collected from hypogonadal women using the standard LER-907 for comparison was 13·25 ± 0·56. This mean ratio was significantly elevated (P < 0·02) above that found for normal cyclic women, 9·48 ± 0·49. After one i.v. injection of 10 μg LH-RH, 5 hypogonadal and 6 luteal-phase women showed an initial significant drop in the B:I ratio (P < 0·05 and P < 0·02 respectively) followed by a steady significant rise (P < 0·03; P < 0·01 respectively). This drop in the B:I ratio as immunoreactive LH rose and the rise in the B:I ratio as immunoreactive LH fell may be the result of the release of two or more kinds of LH, one or more with a slower in-vivo clearance rate and an increased B: I ratio.

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P. F. Daels, S. Shideler, B. L. Lasley, J. P. Hughes and G. H. Stabenfeldt

Summary. Oestrogen secretion was determined by oestrogen conjugate (EC) analysis of urine in three groups of pregnant mares: Group I (N = 6), animals ovariectomized on Day 18–19 of gestation with pregnancy maintained by daily administration of an oral progestagen, altrenogest; Group II (N = 9), untreated, pregnant mares; Group III (N = 5) intact, pregnant mares treated daily with altrenogest.

The mean EC concentrations in the ovariectomized mares in Group I increased in a constant linear manner from 17 ng/mg Cr on Day 20 to 291 ng/mg Cr on Day 70, with no apparent surge in oestrogen secretion around Day 39. Mean EC concentrations on Days 33, 39 and 44 were respectively 41, 48, and 73 ng/mg Cr. In the intact mares in Groups II and III (shown in parentheses), the mean urinary EC concentrations were 201 (171) ng/mg Cr between Days 20 and 33 of gestation, increased rapidly from 172 (77) ng/mg Cr on Day 33 to a peak of 1066 (895) ng/mg Cr on Day 39, followed by a decline to 637 (719) ng/mg Cr on Day 44. After Day 44, EC concentrations continued to increase in a linear manner to 1191 (842) ng/mg Cr on Day 70. The mean EC concentrations between Days 20 and 70 in Group I were significantly (P < 0·05) lower than in mares in Groups II and III. EC concentrations in Group III mares were significantly lower (P < 0·05) than in Group II mares between Days 28 and 34.

We suggest that the ovary is a major contributor to the oestrogen conjugate concentrations measured between Days 20 and 70 and that the rapid increase between Days 33 and 39 is the result of a change in the rate of ovarian oestrogen synthesis.

Keywords: oestrogen; pregnancy; ovary; horse

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J. F. Kirkpatrick, V. Kincy, K. Bancroft, S. E. Shideler and B. L. Lasley

Summary. An enzyme immunoassay for urinary pregnanediol-3α-glucuronide (PdG) was evaluated for the indirect measurement of progesterone metabolites during the oestrous cycle and early pregnancy of uncaptured North American bison. Comparisons between plasma progesterone and urinary PdG, dose–response parallelism between the standard curve and diluted urine samples and high-performance liquid co-chromatography revealed that PdG was a primary immunoreactive urinary metabolite of progesterone in bison. Urine samples were collected directly from the soil from 29 bison cows during the August rutting season and analysed for PdG. Eight bison cows demonstrated complete oestrous cycles ranging from 19 to 26 days (mean cycle length = 23·12 ± 0·76 days) and behavioural oestrus among four of these cows correlated with PdG nadirs. Mean PdG nadirs were 63·62 ± 21·61 ng/mg urinary creatinine (Cr) and mean peak midluteal values were 546·01 ± 130·73 ng/mg Cr. Seven of eight became pregnant, indicating that bison exhibit a second seasonal oestrus. Eighteen other bison cows were pregnant prior to the beginning of the study and demonstrated non-cyclic increased PdG concentrations (>200 ng/mg Cr) during the 30-day course of collection. Three cows ovulated and became pregnant during the 30-day collection period and then exhibited increasing urinary PdG concentrations. This report demonstrates that ovarian function in uncaptured bison can be monitored by means of urinary PdG and that both ovulatory cycles and early pregnancy can be detected.

Keywords: oestrous cycle; progesterone metabolites; urine; bison

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N. M. Czekala, J. K. Hodges, G. E. Gause and B. L. Lasley

Summary. Mean circulating concentrations and seasonal changes in plasma testosterone over 3 years were similar in free-ranging and captive male armadillos. The highest concentrations were seen in the summer months, i.e. at the time of maximum breeding, but the relatively high values at other times and the inability of ACTH to restore dexamethasone-suppressed testosterone concentrations confirms that testicular function continues throughout the year. There was a gradual rise in plasma testosterone to adult levels from the 5th to the 9th month of life in captive-born males, indicating that sexual maturity is reached within the first year of life and that captivity is not deleterious to Leydig cell function.