[Cells secreting hydrogen ions into the renal tubules]

The ultrastructure of the epithelial cells of the renal tubules and of parietal cells of the stomach in intact rats was compared with that in animals with acute metabolic acidosis and animals kept on dry food. The studies were conducted on white male rats weighing 120-150 g. Acute metabolic acidosis was induced by a single intraperitoneal injection of 1 ml of a 1% solution of ammonium chloride. Pieces of the tissue for electron microscopy were fixed with OsO4 and poured with araldit and epon-812. The studies conducted revealed the ultrastructural similarity between the dark cells of the distal gyrous tubule and collecting tubes with parietal cells of the stomach. This similarity was seen from the one-type distribution of mitochondria of the smooth-walled vesicules and appearance in acidosis of intracellular and intercellular tubules. Such cells were not revealed in the proximal tubules, however, consideration of the results obtained and the literature data makes it possible to suggest that all cells of the proximal part of the nephron secret H+-ions, this being one of their functions. In the distal gyrous tubules and in the collecting tube this function is realized by specialized dark cells.