Chronic folic acid-nephropathy.

Investigations with a total of 169 male Wistar-rats led to the result that repeated injections of 250 mg folic acid per kilogram body weight in intervals of 3 weeks cause severe chronic kidney damages. After the 4th folic acid injection the outer surface of the kidneys is roughly granular due to circumscribed destructions of the parenchyma in the cortical area and turns into contracted kidneys, within the 48 weeks of the test. Lesions of tubules and of the interstice, particularly around distal nephron segments (convoluted portion of distal tubule, initial segment of collecting tubule and cortical collecting tubules) and focal atrophies of proximal tubules can be observed microscopically. Apart from this, a significant enlargement of all straight portions of the distal tubules in the outer medulla can be noticed. At the end of the 48 weeks serum urea and serum creatinine are twice as high as standard, the daily amount of urine is ¢ times higher than the control value, the osmolarity of urine is reduced by 60--77%, experimental animals lose essentially more sodium with the urine than control animals.