A new moist chamber respirometer for the study of the metabolism of tissue slices in vitro.

Deficiencies in the classical Warburg tissue respiration technique incident to the immersion and continuous agitation of thin tissue slices in a liquid medium have been long and generally recognized. Rodnight and McIlwain recently have described a modified technique (a), in which the gas exchange of the tissue slice is measured in non-aqueous media or under “moist” aqueous conditions with very small volumes of medium. In the case of some tissues, notably brain and kidney, they observed appreciably higher rates of oxygen uptake than with the usual Warburg procedure. In the course of isotopic tracer experiments on the metabolism of cytochrome c in vitro (l), we found that the recovery of the chromoprotein was very poor when slices of rat liver were incubated at 37” for 2 to 3 hours in appropriate aqueous media. Furthermore, the small amounts of cytochrome c which were isolated necessitated the use of relatively large quantities of radioactive isotopes of high specific activity. To overcome these difficulties, we have designed a new apparatus, based on the “moist tissue” principle (2), which has made possible the incubation of large numbers of tissue slices in comparatively small volumes of medium for periods of time longer than 6 hours, with maintenance of a steady state of oxygen consumption and excellent recoveries of cytochrome c at the termination of the incubation. In this paper the new moist chamber respirometer, which should have many areas of usefulness in studies of metabolism in vitro, is described. Data are furnished from which the inference may be drawn that the metabolic performance of tissue slices in this “moist” method is maintained at an optimal level (as judged by the rate of oxygen consumption) 2