Renal interstitial cell granularity in dogs with renal hypertension.

Hypertension was induced in dogs by the partial occlusion of one renal artery. After 12 days of hypertension the interstitial cells in the medulla of kidneys from hypertensive animals were examined by electron microscopy, and the appearance compared with interstitial cells from normal dogs. The osmiophilic granules in the cells were classified into dark and light forms, and the numbers of each counted in at least 70 cells per kidney. It was not possible to quantify the number of interstitial cells in each renal medulla. The kidneys with partially occluded renal arteries had an increased total number of granules per cell (4.93 +/- 0.51) compared with normal kidneys (0.79 +/- 0.14), and the great majority of these were dark granules (95.3% and 79.5%, respectively). In contrast the contralateral untouched kidneys had a significantly reduced number of granules per cell (0.58 +/- 0.14), and only a small proportion of the total were dark granules (31.1%). The actual number of light granules per interstitial cell was significantly increased in the untouched kidney compared with normals.