Measurements of adipose tissue respiration in a closed chamber using an oxygen sensor: methodological considerations.

A new polarographic system for measurement of oxygen consumption in vitro has been constructed to minimize different types of errors. The system was built of polyamide-6, Monax glass, stainless steel, and rubber to diminish oxygen leakage and gas capacitance properties. With these materials the system was gas-tight. Nevertheless, the incubation chambers had oxygen capacitance properties that had to be corrected for mathematically. Thus, in order to obtain more exact absolute values of the respiratory rate, the apparent respiratory slopes were continuously corrected for delta pO2. Furthermore, the initial slope observed in the absence of biological material was also taken into account. Using these variables, the apparent slope (mm Hg/min) could be adjusted by subtracting the following correction factor: correction factor = 0.00306 X delta pO2 + 0.198 X (initial slope). This correction gave a high degree of linearity and an overall error on the order of 10%. Without the described correction for the oxygen capacitance, the true respiratory rate may be underestimated by up to 50%.