An attempt to measure glomerular plasma flow by the cationic dyes alcian blue and ruthenium red

Autoradiography showed that 3H-labelled alcian blue injected into the rat renal artery was concentrated in the glomeruli. To test if the uptake could be used as a measure of local glomerular plasma flow, the one-pass extraction was measured in 19 rats. The average extraction was 31.9% (SD 8.0%). Impurities and heterogeneity of the tracer as well as reversible binding to erythrocytes may have contributed to the low estimated extraction. The average extraction of 103Ru-ruthenium red was 26.3%. We conclude that neither of these dyes are suitable for measurement of glomerular plasma flow.