Techniques in tissue metabolism. 3. Study of tissue fragments with little or no added aqueous phase, and in oils

Abstract

Respiration of sliced cerebral cortex, kidney cortex, liver and spleen from guinea pig, rat, or rabbit was measured in the presence of minimal aqueous fluid. The tissue rested on a grid in apparatus designed for these procedures. Tissues examined fresh or moist (prepared in saline but drained before use) respired at rates initially similar to or higher than those under conventional conditions which employed 100-1000 times as much aqueous phase. Rates subsequently fell unless substrate was provided. Comparably high respiratory rates were observed with the tissues immersed in a silicone fluid, light liquid paraffin, or olive oil. Substrate was provided either during preliminary preparation of the tissue, or in a non-aqueous phase during metabolism. Inhibitory and stimulating substances were also effective when so added. Respiration of moist cerebral cortex was increased by electrical pulses and the increase opposed by certain added agents. Formation of lactic acid by cerebral tissues in minimal aqueous fluid was closer to its normal in vivo value than was its formation with the conventional excess of saline. A considerable level of phosphocreatine could be maintained in moist cerebral tissues for at least 75 minutes, while they respired at 37[degree] in O2.