Spontaneous arteritis and glomerulitis in mice. A comparison of light and electron microscopic renal changes in PN/n, NZB/BL, 101/MAC, and CBA/MAC mice

Abstract

Four PN/n mice between 12 and 17 months of age had fibrinoid necrosis of the renal arteries, but 32 mice up to the age of 17 months showed no consistent change in the media or intima of the renal arteries although perivascular cuffing with round cells was prominent from 9 months of age. Glomerulitis, indicated by increase in the mesangium on light microscopy, affected most mice over 7 months of age, and dense deposits on electron microscopy were present in most mice from 7 months of age. These changes occurred significantly more frequently than in CBA/MAC mice; the 101/MAC showed an intermediate frequency, and the pattern in a small sample of NZB/BL mice resembled that of the PN/n mice. Basement membrane thickening increased with age from 3 weeks in all of the strains but more often included dense deposits in PN/n mice. Splitting of the glomerular basement membrane in very young mice in all strains was not considered relevant and may have been developmental. Failure consistently to detect glomerulitis earlier by electron microscopy than by light microscopy was attributed to the greater sampling error of the former. Unidentified dense bodies in glomerular epithelial cells occurred at all ages in all strains, so the suggestion that they were virus particles relevant to the disease was not sustained. Intraobserver variation studies showed satisfactory repeatability for light microscopy and for dense deposits and basement membrane thickening, but the dense bodies were not detected with acceptable reproducibility, a difficulty partly due to technical variation.