THE OPTIMAL WATER REQUIREMENT IN RENAL FUNCTION

Abstract

The question of whether or not the optimal water requirement for removal in urine of urea and of several salts (NaCl, KCl and KHCO3) is the same for each of these substances and additive for mixtures of them was studied in a series of experiments by measuring the water intake of young adult rats on a basal diet to which were added successive increments of urea and of salts, singly and together. The data obtained demonstrate that the optimal water requirement for each of the salts is identical, or nearly so, and that the individual requirements are, at least closely, additive; that the quantity of water required for removal of urea is much less than for corresponding amounts (osmolar) of the salts studied; that the differing requirements for urea and salts are not additive, the requirement for a mixture of equal amounts of urea and of salt being the same as for an equivalent quantity of urea alone.