Tracing the accumulation and effects of mercury uptake in the previtellogenic ovary of crucian carp Carassius auratus gibelio by autometallography and caspase-3 immunohistochemistry

Abstract

The aims of the present study were to apply the AMG technique for localization of mercury at the light and electron microscopic level in the ovary of crucian carp after exposure to mercuric chloride and to find out if this heavy metal induces expression of caspase-3. Depending on the stage of ovarian follicle development, two patterns of mercury accumulation have been found in previtellogenic ovary of crucian carp. The first mercury accumulation pattern has been found in the early previtellogenic oocyte without zona radiata. In these oocytes, mercury accumulates into an ooplasmic region that seems to correspond to the Balbiani body (32-65 μm oocyte diameter), throughout the cytoplasm (84-116 μm oocyte diameter) and in the cortical cytoplasm (~180 μm oocyte diameter). The second mercury accumulation pattern has been found in the late previtellogenic oocyte with cortical alveoli (229- 330 μm oocyte diameter). Ultrastructural observations have shown grains of silver-enhanced mercury inside coated vesicles, the cortical lysosome-like bodies or multivesicular bodies and cortical alveoli. Immunohistochemistry reaction for caspase-3 was positive in nuclei of the early previtellogenic oocyte and Balbiani body.