Instantaneous measurement of glomerular filtration rate in the isolated perfused rat kidney

Abstract

In perfusion studies on the isolated cellfree perfused rat kidney, the glomerular filtration rate (GFR) can be controlled if the GFR can be measured instantaneously. This paper reports on a GFR meter which opens this possibility. Vitamin B₁₂ is used as a marker for the GFR. A bubble flow meter determines urine flow rates ranging from 10 up to 200 μl · min⁻¹. A fiberoptic colorimeter measures vitamin B₁₂ concentrations in the urine up to 400 mg · l⁻¹. The flow meter and the colorimeter are described in detail. The reliability of vitamin B₁₂ as a marker for the GFR is demonstrated and, moreover, the identity of GFR values obtained with the GFR meter and those from B₁₂ spectrophotometry is demonstrated.