Folic acid-induced renal injury and repair. Correlation of structural and functional abnormalities.

Folic acid administered to rats in doses of 100, 200, 300, and 400 mg/kg of body weight resulted in alterations in renal tubular morphologic features and renal function, with the severity of the changes proportional to the dose. Renal cell incorporation of tritiated thymidine varied according to cell type and increased with the dose of folic acid. The results demonstrate (1) a spectrum of renal injury and subsequent repair; (2) a reduction in concentrating ability and creatinine clearance proportional to the dose of folic acid in the range of 100 to 300 mg/kg; and (3) increased mitotic activity at high doses of folic acid (300 and 400 mg/kg) of all renal tubular cell types examined, with collecting ducts demonstrating the greatest degree of regeneration. From these observations, we conclude that there is a predictable relationship between the dosage of folic acid and the abnormalities of morphologic features and function in this model of kidney injury.