Ammonia Production in the Collecting Ducts of Mammalian Kidneys

COMPARED with other parts of the nephron, the cells of the collecting ducts are morphologically conspicuous by the absence of any particular differentiation. This has led to the assumption that their function is exclusively mechanical, that is, to convey the urine from the distal part of the nephron to the renal pelvis. Physiologists have not been able to assign any active cellular function to this part of the nephron, though Glimstedt 1 and Wirz 2 presented convincing evidence for its importance in water reabsorption and we have suggested 3 that back-diffusion of ammonia might occur in this segment. Both these functions are presumably of physicochemical nature and independent of cellular activity.