Kinetics of 51CrEDTA in the rat

The kinetics of 51Cr EDTA in the rat has been analysed. A single bolus injection after an equilibration period of 30 min, resulted in a steep monoexponential plasma clearance (T 1/2 = 40.8 +/- 4.3 min). To facilitate estimation of the EDTA space, renal clearance was eliminated by renal vascular ligation. The extrarenal clearance of EDTA was very slow (T 1/2 approximately 800 min) according to a linear function. The EDTA space was 25.7 +/- 1.8 ml/100 g body weight. The EDTA space is considered to measure the extracellular fluid volume.