Some properties of mitochondria isolated from the flight muscle of the periodical cicada, Magicicada septendecim

Abstract

Mitochondria from the flight muscle of the periodical cicada oxidize pyruvate and d-glycerol 1-phosphate at rates comparable with those obtained with flight-muscle mitochondria from other insects. The oxidation of d-glycerol 1-phosphate is greatly stimulated by low concentrations of Ca²⁺. However, oxidative phosphorylation with this substrate is optimum over only a narrow range of Ca²⁺ concentration, because of the ability of these mitochondria actively to accumulate Ca²⁺ present at micromolar concentrations. The oxidation of pyruvate via the complete tricarboxylic acid cycle is enhanced by high concentrations of phosphate. When both pyruvate and d-glycerol 1-phosphate are present simultaneously, there is no simple summation of the rates obtained with the substrates singly. Acetyl-l-carnitine, palmitoyl-l-carnitine, glutamate and 2-oxoglutarate are oxidized at rates similar to those obtained with mammalian mitochondria, though lower than those obtained with the two prime substrates. However, no other tricarboxylic acid-cycle intermediates added to the medium were oxidized. From these and other observations it has been concluded that these mitochondria possess a previously undescribed combination of substrate-anion permeases.