[Renal clearance of hippurate in persons with chronic renal insufficiency]

In 8 subjects with chronic renal failure treated conservatively the renal hippurate clearance (CHip), polyfructosan (CPF) and creatinine (Ccr) clearance was assessed. The mean values of the investigated variables were as follows: CHip = 1.06 +/- 0.79 ml/s, CPF = 0.15 +/- 0.08 ml/s, Ccr = 0.27 +/- 0.17 ml/s. The ratios between the investigated clearance values were: CHip/CPF = 6.9 +/- 4.2 and CHip/Ccr = 4.2 +/- 1.4. The ratio of CHip/CPF was in some instances as high as 10 or more. Between values of CHip/CPF and the plasma hippurate concentration (PHip) a significant negative (non-linear correlation was found (p < 0.01). When the PHip values were very high, the value of the CHip/CPF ratio was close to 1. The recorded findings confirm that in subjects with chronic renal failure in the residual nephrons hippurate is synthetized and its urinary excretion in relation to glomerular filtration is increased. The findings suggest also that in these patients the tubular transport for hippurate is saturated. It will be necessary to take into account the possible saturation of tubular transport for hippurate when interpreting changes of drug excretion (i.e. those excreted by the same mechanism as hippurate) in subjects with chronic renal failure.