Partial prevention of active Heymann nephritis by lα, 25 dihydroxyvitamin D 3

SUMMARY The hormone lα, 25 dihydroxyvitamin D 3 (1,25(OH) 2 DO 3 has potent immunosuppressivc effects in vitro . Recent publications also described a protective effect of the hormone in various animal models of immune‐mediated diseases. To test its in vitro activity we induced active Heymann nephritis in Lewis rats that were either untreated or treated with 1,25(OH) 2 D 3 or its synthetic 20‐epi analogue, KH1060. Treatment with cyclosporine A (CsA) was used as an immunosuppressive control. In this nephrotic model the administration of 1,25(OH) 2 D 3 (0.5 μg/kg body weight) given on alternate days during the first 13 days after active immunization significantly reduced the proteinuria as measured by weeks 7–9. This reduction was comparable to the reduction observed in rats treated with CsA (20 mg/kg) on alternate days. A second series of experiments with 1,25(OH) 2 D 3 confirmed these findings. The level of autoantibodies was found to be significantly suppressed during the treatment time in the CsA (20 mg/kg) group, whereas the limit of significance ( P =0.06) was reached in the 1,25(OH) 2 D 3 groups that developed less proteinuria. The administration of 1,25(OH) 2 D 3 transiently increased the mean serum calcium Concentration with 2.5 mg/dl above the pretreatmcnt values, and the urinary calcium excretion by a factor of 3–5 during the short treatment time. Treatment with the analogue KH 1060 did not reduce the proteinuria significantly. Our experiments add evidence to the hypothesis that 1,25(OH) 2 D 3 in pharmacological doses has immunosupprcssive potency.