l-Arginine normalizes NOS activity and zinc-MT homeostasis in the kidney of mice chronically exposed to inorganic mercury

Inorganic mercury (HgCl₂) exposure provokes damage in many organs, especially kidney. Inducible nitric oxide synthase (iNOS) expression, total NOS activity and the profiles of zinc (Zn), copper (Cu) and Hg as well as their distribution when bound to specific intracellular proteins, including metallothioneins (MT), were studied during HgCl₂ exposure and after l-arginine treatment in C57BL/6 mouse kidney. HgCl₂ exposure modulates differently iNOS expression and NOS activity, increasing iNOS expression but, conversely, decreasing total NOS activity in the mouse kidney. Moreover, during Hg exposure an increased MT production occurs. The kidney damage leads to a loss of urinary proteins, increased plasma creatinine and high Zn mobilization with consequent increased urinary Zn excretion. l-arginine treatment recovers NOS activity and induces a normalization of MT induction, plasma creatinine values and urinary proteins excretion, suggesting that l-arginine may limit kidney damages by Hg exposure.