Effect of Cr(VI) on the Nucleolar Activity in Liver Cells from Odontesthes bonariensis (pisces).

CARRIQUIRIBORDE P.; RONCO A. E.; DULOUT F.N.

Pretoria, South Africa

Simposio; 9th International Symposium on Toxicity Assessment; 1999

Environmentek, CSIR

The nucleolus is a subcellular structure involved in the synthesis of rRNA and therefore related with the cell protein synthesis. The morphology of the nucleolus depends on the metabolic activity condition of this organelle. The present study evaluates nucleolar activity in liver cells of exposed organisms in the laboratory to a Cr(VI) (as dichromate) solution at a concentration level 40 times lower than the acute toxicity level (24h LC50=40mg/l) respect to a control population. The measured parameters were done using fish fry of the local freshwater species O.bonariensis. The tested organisms were divided in 2 groups of 32 individuals each, sampling 8 organisms from each group at 30, 60, 120 y 240 min and fixed with Carnoy. Cytologycal slides of liver tissue were made by the routine air-drying method and stained with 50% AgN03. One hundred cells per individual were analysed at a total magnification of 330X. Nucleoli area was measured using the Acad software, fitting an eliptical form. The measured end points were mean total nucleoli area and mean number per cell for each individual. The average value of the individual mean were used to compare different treatments at each exposure time using T-Student statistical test. Results show that the total nucleoli area per cell present a significant reduction of the area in exposed organisms respect to controls, however the mean nucleolar number remain constant. Significant differences in total nuceolar area appears after 60 min exposure. The easiness to perform of the methodology and low infrastructure requirement, relevance of the end point signal, together with the present results encourage future studies leading to the standardisation of the biomarker.