Disappearance of Mannitol and PAH From Plasma of Bilaterally Nephrectomized Dogs

Abstract

A determination of the volumes of distribution of mannitol, p-aminohippuric acid, and Na thiocyanate and their possible disappearance from the plasma was studied in 17 bilaterally nephrectomized dogs, following a single intraven. injn. of these substances. The volumes of distribution of PAH and thiocyanate were similar, but slightly greater than that of mannitol. Both PAH and mannitol disappeared slightly from plasma. Thiocyanate remained constant. The disappearance of PAH and mannitol was not due to destruction in the body, conjugation, nor dilution of plasma by an ingress of fluid from the tissues. Passage into blood cells occurred with PAH but not with mannitol. Such a disappearance does not occur if bilateral nephrectomy is performed 2 hours or more after these materials have been injected into the body. Hence, in calculating the clearance of mannitol and PAH in intact animals, by use of the slope method, the extra-renal clearance can be ignored, because the extra-renal loss is negligible.