Respiratory Effects of Substituted Phenols at Varying Carbon Dioxide Tensions

Abstract

During a study of the reversible inhibition of cell division which is produced in fertilized marine eggs by certain nitro and halo-phenols 1 , 2 the CO₂ tension was found to be a significant factor in the degree of inhibition attainable. 3 The respiratory effects of substituted phenols were then measured on cells which were exposed to a gas phase containing oxygen and CO₂ in various ratios.

The manometric techniques of Warburg (direct method) and of Dickens and Simer (second method) were employed. 4 Fertilized eggs of the sea urchin (Arbacia punctulata) and a baker's yeast (Anheuser-Busch) served as material. The egg experiments were made at 20°C, using sea water as the suspension medium. This was 0.002 molar in bicarbonate. The yeast experiments were made at 25 °C, using a suspension medium 0.1 molar in glucose and 0.004 molar in bicarbonate.

When the oxygen consumption of either type of cell is plotted against the logarithm of the concentration of a stimulating substituted phenol, the curve rises nearly linearly until an optimum is reached; beyond this optimum concentration the oxygen consumption falls rapidly, nearly to zero. Cell division in the fertilized eggs is inhibited by those concentrations of the reagent which give the falling portion of the oxygen consumption curve. 1 , 5

With fertilized sea urchin eggs in 4, 6-dinitro-o-cresol a change in the partial pressure of CO₂ from the usual atmospheric level, about 0.0005 atmospheres, over a range of tensions up to 0.02 atmospheres, has little effect on the position of the rising portion of the oxygen consumption curve. The falling portion of the oxygen consumption curve is displaced to a lower range of concentrations of the 4, 6-dinitro-o-cresol; the respiratory optimum concentration decreases from 8 × 10^-6 to 10^-6 molar; and the number of units of excess oxygen consumed at this optimum decreases with rising CO₂ partial pressure.