THE EFFECT OF SALT INTAKE ON CYCLOSPORINE-INDUCED IMPAIRMENT OF RENAL FUNCTION IN RATS

Abstract

Three groups of rats were fed a low-Na diet. Group 1 drank water and was treated with cyclosporine, 100 mg kg-1 48 h-1 p.o. for 3 wk (low-salt-treated group). Group 2 drank 0.15 M saline and was also treated with cyclosporine (high-salt-treated group). Group 3 drank water and was treated with the vehicle (low-salt-vehicle group). Measurements were made during a control period and weekly during the 3-wk treatment period and a 3-wk recovery period. Both cyclosporine-treated groups lost weight during treatment but the rises in serum creatinine and blood urea and decrease in creatinine clearance were greater in the low-salt group. The vehicle group gained weight and had no change in the other parameters over the 3 wk. There was an increase in urine volume and Na excretion in the high-salt group associated with cyclosporine treatment. Although the low-salt groups had a higher plasma renin concentration than the high-salt group there were no changes produced by cyclosporine treatment. Histopathological examination showed mild tubular lesions with vacuolar degeneration of proximal tubular cells. This was more prevalent in the low-salt-cyclosporine-treated group. The plasma concentrations of cyclosporine were not different after 1-wk treatment but were slightly greater after 2-wk and 3-wk treatment in the low-salt group. The greater impairment of renal function in the low-salt group produced by cyclosporine may be contributed to by an involvement of tubuloglomerular feedback.