Electronmicroscopic study of renal glomerular lesions in toxemia of pregnancy

Abstract

Kidney biopsies from 14 patients with proved toxemia of pregnancy were examined by light and electron microscopies, based on the histological classification of the glomerular changes by Yajima, in 1966. In the most cases, semi-ultra thin sections from epon-embedded renal tissues after removal of resin, stained by PAM silver impregnation were also examined . Then we observed whole renal architecture in conventional sections and each glomerular structure in semi-ultra thin sections by light microscopy and specific glomerular fine structures in ultra thin sections by electron microscopy . In some typical cases, PAM silver impregnation method for electron microscopy was performed for examinations of the details of basement membrane and mesangial matrix . The results were following. 1. In electron microscopic examination of kidneys in toxemia of pregnancy, it is always indispensable to correlate the electron microscopic findings with light microscopic observations. 2. Even the clinical types in toxemia of pregnancy are varied from each other, the same histological type in light microscopy shows basically the same electronmicroscopic findings . 3. The narrowing of the glomerular capillary lamina is due to swelling and proliferation of endothelial and mesangial cells. The epithelial cells are occasionally increase in number, but they do not take the important role in narrowing of capillary . 4. In the most severe cases, the amorphous depositions of the same electron density as lamina densa of basement membrane are often found in subendothelial space . Occasional depositions are also found in mesangial matrix. These observations seem to indicate the possibility of the passway from subendothelial space to mesangial area . 5. It is of great use to utilize the silver impregnation method for electron microscopy, especially in examination of basement membrane and mesangial matrix . 6. The thickening of the basement membrane is not so outstanding as believed in this disease. When exists, the thickening of the basement membrane is more pronounced in the mesangial areas than glo merular capillaries. 7. "Swelling" and "thickening" of basement membrane are possibly differentiated by utilizing silver impregnation method for electron microscopy . 8. The attitudes of mesangial matrix seems to predict the prognosis or the recurrence of the disease in some extent. 9. The increase of mesangial matrix in clinical " mixed type" of toxemia of pregnancy is more obvious than that of clinical "pure type ". 10. In toxemia of pregnancy with clinical evicences of fore -going other renal lesions, the increase of mesangial matrix is usually outstanding . But the differentiation of those group from recurrent cases is not easy.