VITAMIN-A AND UROLITHIASIS

The effects of vitamin A deficiency on urolithiasis were investigated in male rats. A vitamin A-deficient diet caused important changes in t he composition of the urine of the treated rats when compared with con trols. One of the main effects was a decrease in the concentration of urinary glycosaminoglycans and zinc in the rats receiving the vitamin A-deficient diet. Significant differences were also found in plasma vi tamin E and in the relation of vit E/vit A between treated and control groups but, in general, with no important differences in vitamin A. N evertheless, significant differences in kidney content of vitamin A we re observed between both groups. On the other hand, lesions of the cub oidal epithelium that covers the papillae in rats treated with the vit amin A-deficient diet were severe when compared with controls. The vit amin A and E plasma levels in urolithiasic humans were also investigat ed and compared with those found in a control group. No significant di fferences were observed in plasma vitamin A levels; nevertheless a sig nificant increase in vitamin E and in the vit E/vit A ratio was clearl y observed. These results could be related to a possible deficit of vi tamin A in kidneys of stone formers, this being one of the diverse fac tors that can contribute to urolith development. Moreover, the deficit of important urinary crystallization inhibitors normally found in sto ne-formers, such as pyrophosphate and phytate, can also be related to the presence of low levels of renal vitamin A which prevents the enzym atic degradation of such inhibitors. (C) 1998 Elsevier Science B.V.