Studies of Drugs in Tissue Metabolism. I. Method for Measuring Metabolism of Tissue in Serum

Abstract

The action of compounds of pharmacological importance on the oxidative systems of tissue cells has received widespread attention, particularly through the work of Jowett and Quastel 1 and of Krahl and Clowes. 2 The usual procedure is to determine the metabolism of excised tissue suspended in a balanced salt solution. However, since it might be expected that the respiration of tissue would proceed more normally if the tissue were suspended in a naturally occurring physiological fluid, our attention was first directed to the development of a simple, reproducible method of measuring tissue respiration in serum. A description of this method provides the content of the present paper. Rat liver was chosen as the standard tissue whose respiration was measured, and human blood serum as the nutrient fluid medium in which the tissue was suspended.

Experimental. Indirect methods for determining the respiration of tissue in serum are already available. 3 , 4 However, they have the disadvantage of being complicated and requiring more than the usual equipment for the determination of O₂ consumption by the direct Warburg technic.

The direct measurement of oxygen consumption of tissue in serum has been achieved by (a) alternately acidifying and evacuating serum until its CO₂ content has been reduced to about 0.5 mM per liter (2% of original value); (b) readjusting its pH to about 7.2-7.3; (c) using this CO₂-free serum as the fluid medium in which the tissue is immersed; (d) measuring the O₂ consumption of the tissue manometncally in the Erlenmeyer type Warburg chamber, with absorption of CO₂ by alkali. In this method, the pH of the fluid medium does not change outside the physiological limits, due to the buffering action exerted by the plasma proteins.