Experiments were undertaken to clarify whether a large dose of methylprednisolone (MPSL) had any suppressive effect on rapidly progressive glomerulonephritis in rabbits. Progressive Masugi nephri-tis was induced in 9 rabbits by preimmunization of 400pgN of nephrotoxic duck γ-globulin (NTD) in-corporated with complete Freund's adjuvant into foot pads, followed by intravenous injection of 2 mgN of potent NTD 4 days later. Estimation of urinary protein, serum creatinine and anti-duck r-globulin antibody titer was carried out during the experiment. Serial renal biopsies were performed on the 8 th, 12th, and 15th experiment day and rabbits surviving until the 28th day were sacrificed to examine the histological changes. A massive proteinuria over 1000mg/day developed on the 7 th to 8 th day in all rabbits. Rabbits had the elevation of antibody titer and the rapid increase of serum creatinine up to 10. lmg/dl of average level on the 12th day, resulting in death in 7 of 9 rabbits within 2 weeks. Histologically, serial renal biopsies revealed rapidly progressive glomerular lesions leading to diffuse extracapillary fibrin escape and crescent. In this highly reproducible system of crescent forming glomerulonephritis, rabbits of two groupss were treated with 80mg/kg of MPSL. In one group, treatment started on the 9 th day after the de-velopment of proteinuria, continuing for 6 days and in the other, on the 6 th day before the develop-ment for 9 days. In each group, especially in the latter, antibody titer and serum creatinine level apparently decreased immediately after and during the treatment. Histologically, diffuse prominent intraluminal proliferation appeared in the control group was markedly diminished and crescent forma-tion was not recognized at all during the treatment. About two weeks after cease of treatment, however, rapid elevation of antibody titer and serum creatinine level occured and formation of diffuse crescent was observed. These results suggest that the prevention of processes leading to severe crescentic glomerular les-ions was induced by the treatment with a large dose of MPSL owing to the suppression of antibody production. The further investigation of anti-inflammatory effect of MPSL on severe glomerular lesions will be necessary.
