Improved renal cortical tubule suspension: spectrophotometric study of O2 delivery

Abstract

An improved cortical tubule suspension from the rabbit kidney is described that contains almost entirely proximal convoluted tubules with little contamination by cellular debris or glomeruli. These tubules appear to be capable of active transepithelial transport, since their tubular lumina are open and ouabain inhibits 70% of the QO2 [oxygen delivery]. In previous preparations with closed tubular lumina, ouabain inhibited QO2 only 40% and the base line QO2 was 1/2 to 1/4 that of the present preparation. The delivery of O2 to this tubule suspension was compared to that of slices by 3 different means: O2 consumption kinetics, ATP content, and, more directly by spectrophotometric monitoring of the redox state of cytochrome oxidase. The cortical slice is evidently O2 deficient even when the bath PO2 is in excess of 570 mmHg. The tubule suspension is shown to be adequately oxygenated even at a bath PO2 of 10 mmHg. This tubule suspension will be highly applicable for the analysis of aerobic metabolism in a functionally intact renal preparation by optical, electrode and biochemical assay technologies.