Effect of Cadmium on Water Metabolism Regulation byMeriones shawi(Rodentia, Muridae)

Abstract

In Tunisia, it was reported that Meriones shawi, a desert rodent, was contaminated by heavy metals around several industrial sites. In the present study, the effects of cadmium (Cd) on water metabolism regulation was studied in adult male Meriones shawi that received contaminated diet with cadmium chloride (CdCl2) for 8 days at (1 g Cd/1 L H2O/1.5 kg of granule flour). Expression of arginine-vasopressin (AVP), a crucial hormone for water regulation, was studied by immunohistochemistry in the hypothalamic supraoptic nucleus and paraventricular nucleus. Inspite of variations in water intake, Meriones shawi successfully maintained a balance between water influx and efflux. Cd treatment did not modify water flux rates. Total body water volume remained constant during the treatment in all groups studied. In contrast to what is known in laboratory rodents, water restriction induced an increase in expression of AVP in both supraoptic nucleus and paraventricular nucleus after eight days and two weeks of the experiment, respectively. A similar effect was also observed by treating Meriones with Cd. However, expression of AVP immunoreactivity from deprived water animals in the presence of Cd was markedly and significantly lower than in the absence of Cd. We conclude that Cd exposure modifies the vasopressinergic neuronal system and provides information regarding the neurotoxicity risks that this element presents for mammals and human populations exposed to even low amounts of Cd, without directly affecting water metabolism. Suitability of Meriones shawi as an accumulation bioindicator for Cd was also confirmed in this study.