THE ACTIVITIES OF VARIOUS SUBSTITUTED PHENOLS IN STIMULATING THE RESPIRATION OF SEA URCHIN EGGS

¹ From the William G. Kerckhoff Laboratories of the Biological Sciences, California Institute of Technology, Pasadena, California, and the Marine Biological Laboratory, Woods Hole, Massachusetts

1. Data on the concentrations required for optimum respiratory stimulation and reversible cleavage block in fertilized sea urchin eggs are presented for fifteen different nitro- and halophenols.

2. The experiments show that it is necessary to define the optimum as the highest respiratory increase that does not diminish with time.

3. Cleavage block occurs with concentrations just beyond the optimum defined in this manner.

4. Comparison of the calculated concentrations of undissociated molecules and of anions inside the cell for the different substituted phenols supports the previously expressed view that the anion is the active agent. Penetration is accomplished in the undissociated form, as previously shown.

5. The results of experiments in which the internal pH is raised also support this view.

6. Titration curves of egg brei indicate a high buffer capacity for the egg and support the assumption that the internal pH does not change in the presence of the substituted phenols.