Could the musk compound tonalide affect physiological functions and act as an endocrine disruptor in rainbow trout?

Abstract

In the present study, the effect of polycyclic musk compound tonalide (AHTN) in two concentrations was studied in male rainbow trout (Oncorhynchus mykiss, Walbaum 1792). A feeding trial was conducted with AHTN incorporated into feed granules. One concentration was environmentally relevant (854 µg/kg); the second one was 10× higher (8699 µg/kg). The fish were fed twice a day with the amount of feed at 1 % of their body weight. After an acclimatization period, the experimental phase in duration of six weeks followed. At the end of the experiment, fish were sampled and the biometrical data were recorded. Subsequently, hematological and biochemical tests, histopathological examination, analysis of oxidative stress markers and evaluation of endocrine disruption using plasma vitellogenin were performed. In conclusion, an increase of hematocrit for both AHTN concentrations was found, but no significant changes were observed in biochemical profile. Moreover, AHTN caused lipid peroxidation in caudal kidney tissue, which was confirmed by histopathological images. The long-lasting AHTN exposure could thus be harmful for maintaining homeostasis in the rainbow trout organism. However, the vitellogenin concentration seemed not to be affected by AHTN.

Fig. 1

The concentration of vitellogenin (VTG) in ng/ml in plasma samples after oral exposure to two different concentrations of tonalide (AHTN): AHTN (854 μg/kg) and AHTN2 (8699 μg/kg). Data are given as mean ± SD; n=20/group. No significant changes were found among the tested groups (p>0.05).

Fig. 2

The histopathological findings in skin tissue after oral exposure to two different concentrations of tonalide (AHTN): AHTN1 (854 μg/kg) and AHTN2 (8699 μg/kg). The control group (A) with artificial superficial erosion (black arrow), otherwise without pathological findings. The AHTN2 group (B) with numerous mucinous cells (black arrows). H-E staining, magnification 400×.

Fig. 3

The histopathological findings in caudal kidney tissue after oral exposure to two different concentrations of tonalide (AHTN): AHTN1 (854 μg/kg) and AHTN2 (8699 μg/kg). The control group (A) with normal tubular system and some pigmented deposits. The AHTN2 group (B) with droplet hyaline degeneration of some tubules (black arrows). H-E staining, magnification 200×.