Early manifestation of nephropathy in rats with arterial calcinosis.

In vascular smooth muscle, calcium overload is a highly pathogenic event, which increases with advancing age. An increase in the calcium content of arterial wall may be produced in rats by treatment with vitamin D3. The aim of this study was to evaluate the renal clearance of sulfanilamide (a model organic anion, preferentially eliminated by the kidneys) and other parameters of global renal function in rats with arterial calcinosis. Arterial calcinosis was produced in adult rats by means of a single dose of vitamin D3 (300,000 UI/kg bw, i.m.) 5 days before the experiment. Treated rats showed a large increase in calcium content of aortic tissue and an increase in systolic arterial pressure. No modifications were observed in plasma calcium levels and in plasma lipid profiles. Statistically significant decrements were observed in renal clearance of sulfanilamide, in renal blood flow, in fractional excretion of sodium and potassium. A slight decrease, not statistically different, was observed in the glomerular filtration rate. Rats with arterial calcinosis also showed an increment of total calcium levels in renal tissue, in fractional excretion of calcium and in the expression of organic anion transporter 1 (OAT1). Histological studies revealed tubular alterations. In summary, modifications in hemodynamics and tubular parameters are early manifestations of nephropathy in rats with arterial calcinosis, some of which may account for the changes observed in organic anions renal depuration. It is important to mention that the decrease in clearance of organic anions were seen in spite of the increase in expression of OAT1.