Light and electron microscopical observations on the macula densa of the Syrian hamster kidney

The ultrastructure of the macula densa of the hamster kidney is, in general, similar to that reported for the few other species which have been studied. Their structure indicates that macula densa cells differ in a number of important respects from those of the rest of the thick ascending limb and the distal convoluted tubule. Among these differences may be mentioned the more widely distributed mitochondria with their circular and elliptical profiles; the extensive subsurface vacuolation and the irregular and shallow folds of the basal plasma membrane. Unlike some reports on other species, however, the Golgi complexes were not restricted to an infranuclear position, but were observed in a variety of situations. It was also observed that T-H glycoprotein characteristically associated with the plasma membranes of the cells of the thick ascending limb and the distal convoluted tubule was invariably absent in the macula densa. The possible physiological implications of this and the other observations are discussed.