Abstract
Renal Na excretion correlated well with the product of elevation in plasma Na concentration from original value and GFR, as was suspected from the kinetic model. This was found to be true in the control hypertonic saline diuresis and in the physiologic saline preloading experiment. However, in experiment with aortic constriction correlation was unsatisfactory.
Relative importance of elevation in plasma Na concentration and GFR was estimated by multiple regression analysis. Their importance was similar and original regression equation was verified in the control and the saline preloading experiment. However, in the aortic constriction experiment, while weight for elevation of plasma Na concentration remained unchanged, that for GFR was almost eliminated. This finding may be to explain the reported irrelevance of GFR to renal Na excretion during massive saline diuresis. It is postulated that manipulation of large artery system is the cause of this apparent irrelevance. Further, when GFR was reduced drastically by aortic constriction, renal Na excretion was again larger than was predicted by the regression equation with small coefficient for GFR.
