Tetraethylammonium as a Probe for Estimating Renal Plasma Flow in Unanesthetized Rats 1

Summary Mean total body clearances were measured in unanesthetized rats as Dose iv/AUC in which AUC is the area under the plasma radioactivity disappearance curve for [14C]labeled inulin, PAH, and TEA and also for [3H]inulin. The clearance of inulin radioactivity, either 14C or 3H, was a satisfactory estimate of glomerular filtration rate. The clearance of [14C] radioactivity from labeled TEA was a reliable estimate of renal plasma flow. The renal filtration fraction, which was calculated as the ratio of inulin and TEA clearances, varied from 0.15 to 0.30, with a mean value of 0.21 in the 20 rats in which both clearances were measured simultaneously. Renal plasma flow and glomerular filtration rate can therefore be estimated in the same unanesthetized rat by the clearances of TEA and inulin, calculated as Dose iv/AUC from the disappearance curves of 14C and 3H plasma radioactivity after a single iv injection containing both [14C]TEA and [3H]methoxyinulin.