Corticosterone Inhibition of Pyridine Nucleotide Oxidase from Heart Sarcosomes

Abstract

IT has recently been found in this laboratory that corticosterone is present in higher concentrations in heart tissue than in plasma¹. Since steroid hormones are known to interfere with tissue oxidations, presumably at the level of the flavine enzymes², the relative abundance of corticosterone in heart tissue suggested a study of the effect of this steroid on heart tissue oxidations in vitro. Reduced diphosphopyridine nucleotide was chosen as substrate in order to get the flavine enzymes involved as directly as possible. The enzyme preparation used in the experiments was made from isolated pig heart sarcosomes. These were ground with alumina oxide, suspended in dilute tris-buffer pH 7.4 and centrifuged for 20 min. at 25,000 g. The opalescent supernatant contained an active reduced diphosphopyridine nucleotide-oxidase³ with a specific activity of about 0.1 µmole reduced diphosphopyridine nucleotide oxidized per min. per mgm. protein at 25° C.