RESUMO
The herbicide ioxynil (IOX) and synthetic estrogen diethylstilbestrol (DES) are common aquatic contaminants with an endocrine disrupting action. In juvenile teleost fish IOX and DES disrupt the hypothalamic-pituitary-thyroid (HPT) axis. To assess how IOX and DES influence the developing HPT axis prior to establishment of central regulation of thyroid hormones, zebrafish embryos were exposed to low concentrations of the chemicals in water. IOX and DES (1 and 0.1 µM) exposure failed to modify hypothalamic development but had a negative effect on thyrocyte development. Specifically, IOX and DES caused a significant (p<0.05) reduction in the size of the thyroid anlagen by decreasing the mRNA expression field of both nk2.1a and thyroglobulin (Tg) genes. Inhibition of thyroid gland development by IOX and DES (0.1 µM) was strongly associated with altered heart morphology. To test if the effect of IOX and DES on the thyroid was a consequence of altered cardiac development a morpholino (MO) against zebrafish cardiac troponin I (zcTnI) was microinjected. The zcTnI morphants had modified heart function, a small thyroid anlagen and a reduction in the mRNA expression of nk2.1a and Tg genes similar to that of zebrafish exposed to IOX (1 and 0.1 µM) and DES (0.1 µM). Collectively the data indicate that IOX and DES alter thyroid development in zebrafish and chemicals that alter heart development and function can have an indirect endocrine disrupting action on the thyroid in teleosts.
Assuntos
Dietilestilbestrol/toxicidade , Nitrilas/toxicidade , Glândula Tireoide/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Peixe-Zebra/fisiologia , Animais , Embrião não Mamífero/efeitos dos fármacos , Regulação da Expressão Gênica/efeitos dos fármacos , Coração/efeitos dos fármacos , Hipotálamo/efeitos dos fármacos , Iodobenzenos/toxicidade , Subfamília A de Receptores Semelhantes a Lectina de Células NK/genética , Tireoglobulina/genética , Glândula Tireoide/citologiaRESUMO
An experimental lymphography was effected in 41 rabbits which were given the contrast medium intralymphatically in a dose of 0.3--0.5 ml/kg. The roentgenological dynamics of contrasting the lymphatic structures of the hind limbs and pelvis of the animals was studied. Iodophendylate was found in experimental lymphography to cause no damage to the lymph nodes, lungs, liver, spleen and the kidneys. In the mechanism of the contrast medium elimination of major importance are phagocytic cellular reactions.