Serum and plasma 17-beta estradiol, progesterone and testosterone of dolphins (Tursiops truncatus) by chemiluminescence

Monitoring the sexual cycle in captive animals represents an efficient tool to promote mating, to facilitate the assisted fertilization and to manage specific protocols. In the past the haematological samples obtained from the animals were mainly valued through RIA method, with related radiological danger. On this basis, the purpose of research was to test and validate an innovative and safe method, like the chemiluminescence on serum and plasma samples of Tursiops truncatus. The research was performed on 9 heterogeneous subjects by gender (5 females and 4 males) and age (10-47 years), entertained to Oltremare Aquatic Park of Riccione and to Zoomarine Italia Aquatic Park of Rome. The dolphins were submitted to blood sampling by the tail vein and an ultrasound monitoring, between 9.00 and 12.00 a.m., once a month from April to September. The blood samples were centrifuged to 2500 g/min, frozen to -20°C and then analyzed by using a chemiluminescence method. Data obtained were compared to RIA references data, with the purpose to test and validate this method, through the calculation of the coefficient of variability (CV), and its reliability on serum and plasma samples. An one-way ANOVA with repeated measures was applied to test the effect of time on serum and plasma hormone values. The chemiluminescence method, used to measure the sexual hormones, was precise both on serum and plasma samples, although the use of serum to evaluate 17-β estradiol and progesterone was preferable, with a lowest coefficient of variability. Moreover, the sex hormone concentrations were always ranged within the physiological ranges reported in literature for the Tursiops (1-4) and Whales (5), and related to seasonal and cyclic activity. Mean levels of 17β-estradiol in serum were equal to 135.27±6.82 pmol/L (CV: 5.04%), and in plasma equal to 135.28±11.59 pmol/L (CV: 8.56%); mean levels of progesterone in serum were equal to 0.69±0.05 pmol/L (CV: 7.24%), and in plasma equal to 0.66±0.06 pmol/L (CV: 9.09%); mean levels of testosterone in serum were equal to 44.43±14.42 nmol/L (CV: 33.08%), and in plasma equal to 48,99±12.74 nmol/L (CV: 26.20%). No significant differences were observed between total values of serum and plasma samples and between the different ages, although the adult subjects showed higher 17β-estradiol and progesterone levels than subadult. The highest serum and plasma testosterone variability could suggest that the individual status in social hierarchies might also directly influence this wide range.