Pharmacological studies on experimental nephritic rats (11). Changes in pathohistological and biochemical parameters in anti-rat GBM rabbit serum-induced nephritis

Abstract

Anti-rat glomerular basement membrane (GBM) rabbit serum was produced by immunizing rabbits with the supernatant substance of trypsin-digested rat GBM. Nephritis was induced in rats by a single intravenous administration of 0.25 ml of anti-serum and changes in pathohistological and biochemical parameters during the process of the disease were investigated in comparison with those of Masugi nephritis and the modified type of Masugi nephritis previously reported. In light microscopic studies, histological changes seen in the kidneys closely resembled those of typical human glomerulonephritis. Changes such as hypercellularity, adhesion between capillary wall and Bowman's capsule, crescent formation and hyalinization in glomeruli and interstitial infiltration were the most pronounced on the 30th day after the anti-serum injection. In immunofluorescent studies, a linear fixation of rabbit IgG was observed along the GBM from the 1st day and the staining of a certain intensity was preserved throughout the experimental periods. A linear staining with anti-rat IgG serum was recognized from the 10th day. The fixation of fibrinogen was also seen in not only the glomerular capillary walls, but also in Bowman's space after the 10th day. Proteinuria significantly increased from the 1st day, reached a peak of 12 times the control level, and thereafter gradually decreased. The patterns of progress of urinary alkaline phosphatase and N-acetyl-β-glucosaminidase activities were much the same as those seen in cases of proteinuria and the levels at their peak times were about 10 and 3 times control levels, respectively. Plasma urea nitrogen level transiently increased on the 5th day and then reverted to the control level by the 30th day. Plasma cholesterol levels were significantly high from the 5th to the 20th days. It is concluded that glomerular damages in this model are more severe, so-called, “nephritic type” and continue for longer periods than in cases of Masugi nephritis, however, do not differ in degree and duration from findings in the modified type of Masugi nephritis.