The renal chloride cell of the fresh-water catfish, Parasilurus asotus, with special reference to the tubular membrane system.

The kidney of the fresh-water catfish, Parasilurus asotus, was examined by electron microscopy. A special type of cell, very similar in appearance to the chloride cell of the teleostean gill filaments, is found in the kidney and is referred to as a renal chloride cell. This cell is characterized by an extensive tubular membrane system with a rather constant diameter of approximately 600 A. A number of mitochondria are closely associated with this system. Application of ruthenium red as an extra-cellular space marker revealed that the tubular system is a highly organized derivative of the cell membrane, infolded from the basal and lateral surfaces of the cell. The fine structural resemblance to other types of cells known to possess active transport of electrolytes suggests that these cells are involved in intrarenal osmoregulation.