Efeitos agudos do cloreto de mercúrio sobre a vasculatura renal de ratos

Abstract

Several studies have already been carried to investigate toxic effects of mercury exposure in different systems of the body. There are sufficient evidences showing that, even at low levels, mercury exposure is considered a risk factor for human health. The kidney, an organ of unique importance for clearance and homeostasis of the body fluids, is one of the most affected in mercury intoxication, although little is known about its direct impacts on renal vasculature. Thus, we aimed to evaluate the effects of mercury chloride (HgCl2) infused at different times and concentrations on the isolated renal vascular bed in vitro, and the acute effects of HgCl2 intravenous injection on the in vivo renal function of rats. For this, the left kidney of Wistar rats was cannulated by the artery, removed and conditioned in a perfusion system to evaluate vascular reactivity. Since the flow was kept constant by means of peristaltic pump, changes in perfusion pressure indicated changes in vascular resistance (P = F × R). Experimental protocols were done after infusions of nutrient Krebs-Henseleit solution alone (as controls) or containing HgCl2 at 3, 30 or 300 nM for 30 or 90 minutes. Mercury continuously increased the perfusion pressure only with 300 nM HgCl2 starting from 30 until 90 min; decreased vasodilatation to acetylcholine and decreases vasoconstriction to phenylephrine in a time-and concentration-dependent manner; and increased the perfusion pressure rising as a function of increased flows (flow-pressure curves) after 30 and 90 min of perfusion at 300 nM. The 90 min infusion with HgCl2 cursed with Hg deposits proportional to the concentration used, mainly in the renal cortex. In the in vivo experiments, HgCl2 injection (0,0656 mg/kg) reduced renal blood flow and increased renal vascular resistance, decreased glomerular filtration rate, and increased diuresis and excreted water fraction. These results help to clarify the mechanisms by which mercury exerts toxic effect on the renal system, modifying its vasculature and then hemodynamics.