Effects of cadmium chloride on glial cells of lizard Podarcis sicula.

Cadmium (Cd) is a heavy metal, highly toxic and its levels in the environment are increasing due to industrial activities. It is known that an acute exposure to Cd produces toxicity to the lungs, testes and brain, while chronic exposure determines renal dysfunction, anaemia and osteoporosis. It can cause damages to the nervous system, to the immune system and in some cases to have carcinogenic effects. The brain is an organ that concentrates metals, and these metals are often localized in the astroglia, the first cells of the brain parenchyma to encounter metals crossing the blood-brain barrier. In mammals some studies have been carried out on the toxic effect of heavy metals on glia, thanks to which it has been possible to observe that metals like Cd, Tl, Zn e Pb induce morphological changes in the populations of glial cells. The scope of the present study has been to observe the possible morphological changes induced by CdCl2 on the glia of a reptile, the lizard Podarcis sicula. The reptilian class of vertebrates has been relatively understudied in the field of ecotoxicology, although it is considered to be suitable as bioindicators of chemical exposure due to their persistence in a variety of habitats. In this work 12 adults specimens of Podarcis sicula were exposed to an acute treatment by an intraperitoneal injection of a single and massive dose (2mg/Kg-BW) of CdCl2 and were sacrificed after 2, 7 and 16 days. Serial sections of the whole brains were processed for routine histological and immunohistochemical staining by ABC technique and the anti-GFAP antiserum at the dilution working of 1/100. GFAP (glial fibrillary acidic protein) is the intermediate filament of glial cells and the most widely accepted marker for glial differentiation. Results: in the brain of the reptile Podarcis sicula the general pattern of the GFAP-immunoreactivity was fundamentally represented by long and thick fibres which ran from cell bodies located at the ventricular surface to the meningeal layer. Numerous GFAP-immunopositive structures were observed in the mesencephalon and in the medulla oblongata, but thin fibres GFAP(+) were also present in the telencephalon. The most numerous glial cells observed were of radial glia. In the grey matter of the cerebellum an intense immunoreactivity was observed, while round cells with wide marked cytoplasm were localized in the white matter. After 2 and 7 days the treated lizards showed an decrease of the GFAP-immunopositive structures. After 16 days these reduction of immunostaining was most considerable. The reduction of the presence of the radial glia was most meaningful in the cerebellum and in the optic tectum. This preliminary results show that in the lizards an acute exposition to cadmium provokes decrement of the expression of GFAP marker with possible consequent damage in the function of the glial cells.