Cytoplasmic granularity of the renal medullary interstitial cells in experimental hypertension.

Abstract The renal medullary (papillae and medullae) interstitial cells have prominent features suggesting an actively secretory cell. These include the presence of numerous mitochondria, prominent Golgi bodies, smooth-surfaced endoplasmic reticula, and osmiophilic granules which are stained for neutral lipids with oil Red-O. The interstitial cells were studied as a possible production site for the antihypertensive factor-a neutral lipid. Experimental hypertension was induced in Sprague-Dawley rats by administration of excessive sodium chloride or by injections of DOCA or with a combination of both agents. The same agents were administered to separate groups of animals with and without unilateral nephrectomy. The granularity within 100 interstitial cells was evaluated quantitatively in 0.5 μ sections stained with methylene blue and azure II. Granules within interstitial cells were also counted in electron micrographs of 50 cells chosen at random. Hypertension developed in a significant number of animals after administration of DOCA and also after administration of saline with DOCA, in both uninephrectomized and non-nephrectomized animals. Animals were more susceptible to experimental hypertension following unilateral nephrectomy. Ultrastructural studies of the renal medullary interstitial cell in control animals revealed a relatively constant number of cytoplasmic granules (8.8 ± 1.2). In animals undergoing unilateral nephrectomy and given NaCl with DOCA, the osmiophilic granularity was significantly increased (p