SEX-DEPENDENT HISTOMORPHOLOGICAL CHANGES IN THE THYROID GLAND OF JUVENILE CAIMAN LATIROSTRIS PRENATALLY EXPOSED TO ENDOSULFAN

SCHUERI, F.D.; TAVALIERI, Y.E.; LUQUE, E.H.; MUÑOZ DE TORO, M.; GALOPPO, G.H.

Mar del Plata

Congreso; JOINT MEETING SAIC SAB AAFE AACYTAL 2023; 2023

Sociedad Argentina de Biología

Endolsulfan (END), a banned persistent organochloride pesticide with thyroid-disrupting properties, has been detected in Caiman latirostris eggs collected near crop fields in Argentina. Our aim was to identify potential long-lasting effects of in ovo exposure to END on the thyroid gland of C. latirostris. Eggs from areas with low human intervention were incubated at male or female producing temperature and exposed to 20 ppm of END or ethanol (VEH). At juvenile stage, thyroid glands were extracted, processed, and paraffin embedded. Microscopic assessment of thyroid sections stained with PAS was employed to quantify the percentage of follicles exhibiting varying degrees of hyperplasia (from 0 to 3), according to morphological criteria established by Galoppo et al. (2020). Our results, presented as mean ± SEM, demonstrate that in males, END exposure increased the percentage of follicles exhibiting grade 3 hyperplasia (8,44±4,76 vs 61.30±4,60; p=0.0006). This hyperplasia correlates with higher percentages of follicles displaying over three epithelial layers (8,19±3,80 vs 35,40±6,17; p=0.0037), infoldings (10,90±6,40 vs 32,27±7,21; p=0,0047) and branching (2,99±1,34 vs 47,94±5,11; p=0.0003). These features are indicative of follicle growth, rather than follicle formation. No significant differences were observed in END-treated females. Previously, we reported that END exposure reduced triiodothyronine (T3) levels in males, but increased thyroxine (T4) levels in females. Thus, our findings suggest that in males, follicular hyperplasia could arise from increased TSH stimulation due to diminished T3 levels. In females, elevated levels of biologically less active T4 would likely have a less pronounced impact on TSH levels and thyroid histofunctional characteristics. In conclusion, in ovo exposure to END appears to exert a persistent disruptive influence on thyroid homeostasis, which differentially affects peripheral conversion of T4 into T3 in males and females.