STUDIES ON RENAL HYPERTENSION

REPORT 4. ELECTRON MICROSCOPIC STUDIES ON EXPERIMENTAL RENAL HYPERTENSION

Abstract

Electron microscopic studies were made of the glomerulus and proximal convoluted tubule of 21 rabbits, either normal or Goldblatt-treated, together with observation of blood pressure and renal function. Kidneys were observed at the acute stage of one week after the treatment and in the chronic stage between 30 and 120 days after the treatment in the both groups of elevated and non-elevated blood pressure, comparing with the normal.
The results are as follow.
1) The fine structure of the normal rabbit glomerulus and proximal convoluted tubule were in general agreement with the results published hitherto in several animals.
2) In the Goldblatt-treated rabbit, the glomerular endothelial cell changes slightly in fine structure. In the endothelial filtration layer, the fusion of pores, the separation of the layer from the basement membrane and it's thickening were observed in all stages, particularly at the acute stage. The thickening of the lamina densa was noted only in the elevated group in blood pressure, while it did not occur in the non-elevated group. The thinning and thickening of the inner cement layer and it's separation from the lamina densa were observed in any cases irrespective of the elevation of blood pressure. These changes, however, went back to normal with the passage of time only in the non-elevated group. The outer cement layer remained without disturbance in both group. The proliferation of epithelial cells were often revealed. On the other hand, the shortening and construction of the foot processes and the separation from the basement membrane were observed not only in the elevated group, but also in the non-elevated group. These changes gradually bacame normal with the passage of time in the non-elevated group. The morphological changes of mesangial cells occured in all the rabbits of the elevated group and in about half of the non-elevated group. Only slight changes were observed in the epithelial cell and the basement membrane of Bowman's capsule in both groups. The proliferation of the Juxta-glomerular cell and increase number of the specific granules in these cells were observed in each case of the acute as well as the chronic elevat ed group. However there was no correlation between these changes and the results of renal function test.
3) In the proximal convoluted tubule of the Goldblatt-treated kidneys, the arrangement of microvilli of the brush border were irregularly disturbed and destroyed imcompletely. The urinary space, accordingly, opened widely in both groups, in spite of no change in the basal intususception. The mitochondria showed a decrease in number of the normal type and an increase in number of the vacuolar type both in the acute and chronic stages of the elevated group. There was no correlation btween the changes of mitochondria and results of renal function. It was noted that the basal membrane in the elevated group eminently thickened and became rough. These changes were gradually intentified with the passage of time.
In conclusion, there was no specific finding for understanding the mechanism of elevation of blood pressure by Goldblatt's treatment in this experiment. However, it was cosnidered from the results that the mechanism of elevation of blood pressure may be associated with the thickening of the lamina densa of the glomerular capillary loop and the basal membrane of the proximal convoluted tubule. It was unknown yet why a decrease in number of normal mitochondria and an increase in number of the vacuolar mitochondria in the proximal convoluted tubule occured characteristically in the both elevated groups.