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Summary. LH and testosterone levels in bull calves were studied in the plasma samples collected sequentially at 15-min intervals every month during the first year of life. An episodic pattern of LH release occurred after birth and the frequency and magnitude of the LH peaks increased up to 4 months of age and decreased thereafter. A testicular response was not observed before this age. It is suggested that this episodic LH activity is responsible for the testicular development which then initiates puberty.
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Blood samples and testes were collected from long-finned pilot whales (Globicephala melas) off the Faroe Islands at irregular intervals over a period of 3 years (July 1986–December 1989). Changes in testis mass (n = 674) and plasma testosterone concentrations (n = 214), measured by radioimmunoassay, were examined with respect to age, bodylength and bodymass of the animals. Corresponding to a rapid testicular growth (from 0.25 kg up to 1.9 kg), puberty occurred in male pilot whales of 4.6–5.7 m in bodylength, 1.2–1.9 tonnes in bodymass and 11–22 years of age. Changes in plasma testosterone concentrations confirmed this result, with very low values (< 2 ng ml−1) in immature animals (testis mass < 0.2 kg), followed by a sharp increase (from 2 to 29 ng ml−1) during the pubertal period, and the maintenance of high concentrations with large variability (> 1.5 ng ml−1 to 14 ng ml−1) in mature males. Testosterone concentrations were significantly correlated with testis mass (P < 0.001), but not with bodylength or age, and very large individual variations were observed in mature males. The average age, length and mass at the attainment of sexual maturity were estimated at 16.99 ± 0.30 years, 5.162 ± 0.013 m and 1.403 ± 0.005 tonnes, respectively.
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Summary. A double-antibody heterologous radioimmunoassay (RIA) was developed to measure plasma LH values in hedgehogs. This RIA system used anti-rat LH serum and rabbit LH (AFP-559B) for radioiodination and as standard. The accuracy of the method was evaluated and indicated the ability to detect various relative concentrations of LH in plasma. The minimum detectable dose was 0·2 ng/ml. The intra- and inter-assay coefficients of variation were 4·2 and 7·9% respectively. Biological tests, e.g. effect of castration, effect of castration + testosterone implant and GnRH administration, confirmed that this method was suitable to determine subsequent changes in pituitary gonadotrophic activity in the hedgehog. LH concentrations were determined in blood samples obtained during 1 year: (a) each month, at 4-h intervals during 24 h, from different groups of unanaesthetized animals fitted with a catheter and (b) twice a month, under a light anaesthesia, from the same group of 6 animals. During the year: (1) the range of LH change was narrow (minimum values ≃0·25 ng/ml and maximum values ≃2·00 ng/ml); (2) the 24-h LH patterns did not exhibit any daily rhythm; (3) a clear annual rhythm was observed with the highest values from February to April and the lowest values in October and November. LH decreased rapidly at the end of summer and increased progressively from December to February, during hibernation. In these experiments, it was not possible to determine the characteristics of LH release patterns in the hedgehog but individual profiles indicated clearly the episodic secretion of LH, particularly during the highest pituitary activity period. During the year, a close relationship between the seasonal cycles of plasma LH and testosterone was observed.
Keywords: hedgehog; LH; testosterone; daily variations; seasonal cycle
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The relationship between the corpus luteum and the uterus in terms of the secretion of oxytocin and PGF2α was investigated in free-living and captive roe deer Capreolus capreolus. During the breeding season the corpus luteum contained oxytocin and oxytocin–neurophysin mRNA, and secreted oxytocin in response to administration of the PGF2α analogue cloprostenol. The oxytocin receptor was present in the uterus during the breeding season and during delayed implantation; however, in contrast to the situation observed in other ruminants in which it has been studied, administered oxytocin did not stimulate uterine secretion of PGF2α. Trophoblast interferon was undetectable at any stage of conceptus development. The absence of the mechanism underlying episodic uterine secretion of PGF2α during luteolysis, which may account for the monoestry of roe deer, is consistent with the previously observed luteolytic effect of the PGF2α analogue.
