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.