THE RETENTION AND EXCRETION OF CONTINUOUSLY ADMINISTERED SALT SOLUTIONS

Abstract

From expts. on steady oral ingestion in man of salt solns. of varying conc. the threshold of retention of chloride (expressed as NaCl) is approx. 6 mg./ml. Two other critical concs. were detd. at which neither Cl nor water is retained relative to the other from administered solns. The lower, the minimal isorrheic conc. is 1.4 mg./ml. The higher, the limiting isorrheic conc. is 17 mg./ml. The initial fluid retention following adm. of physiologic and slightly stronger saline solns. is shown to be chiefly a retention of water and not of salt. For intravenous infusions of NaCl solns. in dog, the ratio of fluid output rate to intake rate may be estimated from a theoretically derived equation of steady state. For Cl and probably certain other substances there is reason to believe that the "leakage" conc. in urine forming under steady water intake, may be approx. 1/5 of its normal plasma conc. (uncorrected for extra-renal loss). The threshold of retention of these substances may not be a fixed value even in the normal state, but may fluctuate about a mean.