Reagents Modifying Stimulating Action of 2,4 Dinitrophenol. ∗

Abstract

That 2-4 dinitrophenol (DNP) stimulates endogenous O2 uptake and inhibits phosphorylation in living intact cells and their homogenates seems fairly well established (1). A wide variety of biological materials has been employed in arriving at such a conclusion. Certain differences in reaction of intact cells and their honzogenatcs to the reagent, however, suggest the possibility of additional mechanisms entering into the above reactions. The present results have to do with a study of the action of DSP on the endogenous 0₂ uptake of intact embryonic cells of the grasshopper (Melanoplus dijerctztialis) and the effects of various reagents on such a reaction.

As previously shown from this laboratory (2), mitotically blocked intact embryonic cells respond to a greater degree than similar mitotically active ones. Such differential reactions to the reagent have also been pointed out for other tissues showing different degrees of metabolic activity(1). It has also been shown for intact embryos of the grasshopper that the concentration (5 × 10⁻⁵ 11) of DSP producing maximal stimulation of endogenous 0₂ uptake when added to the homogenate of the embryos produces no change whatever in its endogenous O2 uptake. A somewhat similar situation has also been reported for the ova of the sea urchin(3). Since detergents are highly surface active compounds and have also been suggested to interfere with phosphorylation phenomena (1) it seemed desirable to determine their effects on the endogenous O₂ uptake of embryos and homogenates and also to see to what extent they might modify the stimulating action of DSP.

Results. In Table I are shown data for the effect of duponol and aerosol OT on the stimulating action of DKP on the endogenous 0₂ uptake of intact diapause embryos. An inspection of this table shows that both detergents in appropriate concentrations completely antagonize the stimulating action of DSP. Determinations of phosphates have been carried out by the method of Sumner(4) and it is of some interest to note differences in the reactions of DSP and detergents on the labile phosphorus.