Energy metabolism in Cotugnia digonopora and the effect of anthelmintics

Incorporation of 32Pi into organic phosphate by mitochondria of Cotugnia digonopora was supported maximally by malate. Fumarate and succinate induced lower but significant production of ATP. Pyruvate, alpha-ketoglutarate and oxalacetate proved to be poor substrates and citrate and isocitrate had no effect. A net phosphorylation of approximately 2 mol of ADP was observed for each mol of CO2 liberated from malate or succinate. In contrast, with pyruvate, in spite of a high rate of decarboxylation, the production of ATP was extremely low. 2,4-Dinitrophenol inhibited phosphorylation. All anthelmintics examined interfered with the mitochondrial phosphorylation of ADP, with maximum inhibition by salicylanilide compounds. The anticestodal activity of the latter group of compounds, niclosamide for example, may, therefore, be attributed to their ability to inhibit mitochondrial phosphorylation.