Cadmium and Lead Toxicity, Modulating Roles of Age and Trace Metals on Wistar Rat Cortical Cells

Abstract

The role of age and concomitant exposure to trace elements on Wistar rats was investigated in this study. Fifteen 12 weeks old rats divided into groups A, B and C, and fifteen 36 weeks old rats divided into groups D, E and F were acclimatised for 2 weeks. Groups A and D served as the control groups and were administered distilled water. Groups B and E were administered 1 mL each of 5 ppm, while groups C and F were administered 1 mL each of 10 ppm of lead, cadmium, copper and zinc solutions daily for 1 week. Rats were sacrificed by cervical dislocation and the harvested cerebrum was digested in HNO3 and HClO4. Quantification of metals was done using Flame Atomic Absorption Spectrophotometer. A 5 µm thick paraffin section of the cerebrum obtained at the level of the optic chiasma was stained with H&E and evaluated. Zinc concentration was markedly reduced while cadmium and lead concentrations were increased in both experimental groups across the age groups in a dose-dependent fashion. Copper concentration was reduced in rats with 5 ppm exposure while in those with 10 ppm exposure it was similar to the control. Pyknotic glial cells were more and widespread in the younger rats but few and restricted to the mid-cortical region in older rats. Early neuronal necrosis was widespread in older rat group but restricted to internal granular layer in young rats. Central neuronal chromatolysis was noted in both groups of younger rats but restricted to the 5 ppm group of older rat group. Cerebral concentration of zinc was reduced in cadmium and lead exposure. Glial cells pyknosis were widespread in older rats, but early neuronal necrosis was more widespread in younger rats, showing that the cellular effect of heavy metal is age dependent.