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Toxic glomerulosclerosis-morphology and pathogenesis. Light and electron microscopic studies fo the glomerular
Abstract:
75 male rats were given toxic dosage of the hepatotoxin N-nitrosomorpholine (NNM) using varied concentrations over varied time intervals. During and after the toxic dosings the kidneys were examined by light and electron microscopy in order to decide, whether the kidneys are also damaged by NNM. Our studies reveal that under the influence of a low concentration of NNM a distinct thickening of the GBM and an increase of the mesangial matrix occurs (changes referred by us as glomerulosclerosis). When a high concentration of NNM was given, toxic lesions of the mesangial and epithelial cells of the glomeruli were found, but a glomerulosclerosis was not observed during the intoxication. After this toxic dose was stopped, however, a progressive glomerulosclerosis did develop, which at first was accompanied by a transient proliferation of the mesangial cells. The glomerular changes found in the course of poisoning with NNM were interpreted as a direct effect of the NNM. From studies of the formal pathogenesis of the glomerulosclerosis presented here one can conclude that the poisoning leads to a decrease in breakdown of the components of the basement membrane and the mesangial matrix, thus causing the widening of the GBM and the augmentation of the mesangial matrix.
Insights
N-nitrosomorpholine (NNM) causes kidney damage, specifically glomerulosclerosis, in male rats. High NNM doses initially cause cell lesions, followed by progressive glomerulosclerosis due to impaired matrix breakdown.
Area of Science:
- Nephrology
- Toxicology
- Pathology
Background:
- Hepatotoxins can induce extrahepatic organ damage.
- N-nitrosomorpholine (NNM) is a known hepatotoxin.
- The renal effects of NNM require further investigation.
Purpose of the Study:
- To investigate the nephrotoxic potential of N-nitrosomorpholine (NNM).
- To characterize the glomerular changes induced by NNM exposure in male rats.
- To elucidate the pathogenesis of NNM-induced glomerulosclerosis.
Main Methods:
- Administration of varied concentrations and time intervals of NNM to 75 male rats.
- Kidney examination using light and electron microscopy during and after NNM exposure.
- Histopathological analysis to identify glomerular alterations.
Main Results:
- Low NNM concentrations induced glomerulosclerosis, characterized by glomerular basement membrane (GBM) thickening and increased mesangial matrix.
- High NNM concentrations initially caused toxic mesangial and epithelial cell lesions, without immediate glomerulosclerosis.
- Following cessation of high-dose NNM, progressive glomerulosclerosis developed, accompanied by transient mesangial cell proliferation.
Conclusions:
- Glomerular changes observed during NNM poisoning are a direct effect of the toxin.
- NNM-induced glomerulosclerosis results from decreased breakdown of GBM and mesangial matrix components.
- This impaired matrix turnover leads to GBM widening and mesangial matrix augmentation.