Radiation nephritis and anaemia: a functional assay for renal damage after irradiation

Due to the special radiosensitivity of the kidney it is frequently a limiting organ for regional radiotherapy in nearby sites. In spite of the importance of the organ, there have until recently been few methods for the serial follow-up of renal damage in small animals. In larger animals it is possible to use welldeveloped functional dynamic measurements such as renal blood flow, glomerular filtration rate, and tubular absorption maxima. Recently Williams and Denekamp (1983) have reported on two sequential non-destructive methods for the evaluation of tubular and glomerular function in mice. These methods should be equally applicable to other small rodents. The methods are firstly, the determination of the residual blood radioactivity 1 hour after injection of 51*1Cr-EDTA, a parameter related to glomerular filtration rate, and secondly, urine output as measured by the method developed by Stewart et al (1978) for assaying radiation induced bladder damage. In the course of using the EDTA clearance assay we observed that a complication of this method was the anaemia which has long been known to accompany renal insufficiency in man and other species, whether the nephropathy is radiation-induced or arising from other causes (Rubin & Casarett, 1968; Kunkler et al, 1952; Luxton, 1953; Stewart, 1967). As the anaemia develops, the reduced haematocrit in irradiated animals may introduce significant bias into the estimation of 1-hour clearance of 51Cr-EDTA, since this label would be expected to be entirely confined to the plasma.