Determination of renal reserve capacity by identification of kinetic systems

A method of adapting two-compartment models to dynamic marker concentration profiles for the determination of renal clearance and of its acute changes due to protein ingestion in patients with essential hypertension is descri bed. In 9 healthy controls glomerular filtration rates (GFR) and effective renal plasma flows (ERPF) (ml/min/1.73 m(2): means +/- sd) rose significant ly tested pairwise from 118.2 +/- 13.9 to 139.5 +/- 30.9, p = 0.023 and fro m 503.2 +/- 75.6 to 558.3 +/- 96.2, p = 0.013, respectively. Four patients with mild hypertension and mean arterial pressure (MAP) of 106 +/- 3 mmHg ( duration = 13.8 +/- 10.3 years) showed rises in GFR (73.9 +/- 14.7 to 83.6 +/- 17.4, p 0.034) after stimulation, whereas 6 patients with a MAP of 119 +/- 3 mmHg (duration 17.5 +/- 13.7 years) exhibited 'paradoxical' decreases in GFR (113.3 +/- 18.7 to 103.0 +/- 14.3, p = 0.037). The ERPFs showed non significant changes in the first group of patients (277.8 +/- 52.6 to 323.9 +/- 42.8), whereas the second group revealed increases in ERPF (430.7 +/- 134.5 to 502.3 +/- 113.1, p = 0.013). All patients had normal serum creatin ine levels. The study demonstrates that modern system identification of kin etic experiments, but not traditional techniques relying on steady-state da ta, allow one to detect such dynamic alterations as measures of renal funct ional reserve.