“Efecto del pesticida organoclorado endosulfán sobre el eje hipotálamo-hipófisis-gónada en larvas del pez autóctono Cichlasoma dimerus”.

Y. PIAZZA; M. PANDOLFI; F. LO NOSTRO

Mar del Plata, Argentina

Congreso; II Congreso Argentino de la Sociedad de Toxicología y Química Ambiental (SETAC)(VI Reunión SETAC en Argentina).; 2008

Organochlorine pesticides are widely used to eradicate pests and to improve agriculture. They have been shown to exert a neurotoxic effect on fish, and can cause haematological and histological alterations, and affect the migration of the primordial germ cells. Endosulfan (ES) is still used in Argentina to control insects in commercial crops. C. dimerus is a differentiated gonochoric species, in which differentiation of gonads occurs at 42 days post-fertilization (dpf) in females and at 72 dpf in males. For both sexes, the onset of the differentiation process coincides with the detection of GnRH (gonadotropin releasing hormone, variant 1) immunoreactive (-ir) fibers in the neurohipophysis. These fibers establish a connection with FSH-ir cells in the adenohypophysis. The aim of this study was to analyze the effect of the pesticide ES on the hypothalamus-pituitary-gonad axis in sexually undifferentiated larvae. 2 dpf larvae were exposed to environmentally relevant concentrations of ES (0,03; 0,1 µg/l) for 30 days. Head and trunk were fixed in Bouin´s liquid and processed for histology procedures: immunohistochemistry and Masson trichromic respectively. The number, area and mean cytoplasmic and nuclear diameter of FSH-ir cells and GnRH II and III -ir neurons were measured. At the end of the experiment, none of the animals showed sexual differentiation or any noticeable morphological changes; therefore ES would not be responsible of accelerating differentiation. The mean number of GnRH II and III neurons was 7 and 30 respectively, with no significant differences between control and exposed treatments. The diameter of FSH-ir cells was greater in treated fish, when compared to control fish, possibly reflecting an increased cellular activity. Cell area/nuclear area relation of FSH cells was smaller in treated animals, which would indicate an increased release of the FSH-β protein, given that if accumulation had occurred without release, the cell area would be bigger and hence the relation mentioned before will also be bigger.