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 described. In 9 healthy controls glomerular filtration rates (GFR) and effective renal plasma flows (ERPF) (ml/min/1.73 m(2): means +/- sd) rose significantly tested pairwise from 118.2 +/- 13.9 to 139.5 +/- 30.9, p = 0.023 and from 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 nonsignificant 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 creatinine levels. The study demonstrates that modern system identification of kinetic experiments, but not traditional techniques relying on steady-state data, allow one to detect such dynamic alterations as measures of renal functional reserve.
glomerular filtration rate renal functional reserve pharmacokinetics