engleski

Associations of contaminant metal(loid)s with reproductive hormones in the hair of European brown bear from Croatia and Poland

The terrestrial habitat is contaminated with non- essential metal(loid)s (e.g. arsenic, cadmium, mercury, lead) known to have potential for endocrine toxicity, among others adverse health effects. Impairment of the hypothalamic-pituitary- gonadal (HPG) axis, including steroid hormone homeostasis, may heavily impact individuals and populations, while depleting reproduction, development and adaptation to environmental stress. Organic and inorganic (mercury) pollutant- related changes in reproductive hormones in ursids have thus far been investigated and reported only for polar bear populations. We investigated associations of hair arsenic, cadmium, mercury and lead with progesterone and testosterone levels, taking into account biological and sampling- related variables in two populations of free- living European brown bear (Ursus arctos), Dinara- Pindos (N=46) and Carpathian (N=27), captured during the 2010-2019 period. Metal(loid)s were quantified using inductively coupled plasma mass spectrometry (ICP-MS) and hormones were measured via enzyme immunoassay (EIA). The best among generalized linear models (GLM) constructed with the above predictor variables were selected comparing the Akaike Information Criterion (AIC) values. For progesterone in hair, the breeding period and body condition index (BCI), but not metal(loid)s were significant variables explaining 24% of variation. As expected, cubs and yearlings exhibited lower progesterone then subadult and adult bears in both the non-breeding (beta=0.427, 85% confidence interval - CI: 0.207 to 0.646) and breeding period (beta=-0.295, CI: -0.407 to -0.183). Bears with higher BCI appeared to have lower progesterone in hair (beta=-0.062, CI: -0.100 to -0.025). Hair testosterone variation (30%) was explained by the hair growth period (beta=0.065, CI: 0.319 to 0.097 ; higher testosterone in growth phase compared to quiescent phase), Hg (beta=0.036, CI: 0.006 to 0.065), interaction of age and Pb (beta=-0.948, CI: -1.54 to -0.360) and interaction of Pb and Cd (beta=0.903, CI: 0.080 to 1.73). Our findings confirmed the well-known influence of biological variables on reproductive hormones, and pinpointed complex interaction of contaminant metal(loid)s with brown bear testosterone levels.

progesterone ; testosterone ; non-essential metal ; Ursus arctos ; pollutant

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