A critical analysis of the tissue slice method in manometric experiments

Abstract

O2 uptake of mouse kidney was examined, without addition of substrate and in presence of glucose, lactate, pyruvate, fumarate, citrate, succinate and boiled yeast extract, under varying O2-ten-sions in absence of CO2 and in 95% O2 + 5% CO2. The oxidation rate in absence of CO2 falls off, and incubation without substrate decreases the ability of tissue slices to oxidize substrates which are added later. The decrease of the oxidation rate in absence of added substrates is greater at higher O2 tensions than at lower tensions. The rate of O2-uptake in presence of added substrates expressed as function of the O2-tension changes with time in a way peculiar to each substrate. The presence of CO2 stabilises the O2-uptake of tissue slices in presence of substrate, and safeguards the ability of tissue slices to oxidize substrates which are added afterwards. A steady Q02 however does not indicate a similar steadiness of other reactions (only the final concs, of which have been detd.) occurring during the exptl. period, as demonstrated by the change of R.Q. and Qa with time. Measurements of R.Q., in order to have physiological significance, should not be extended for more than 15-30 mins. The use of tissue mince for the study of oxidative metabolism is also discussed.