The Partition of Flavins in the Heart Muscle Preparation and Heart Mitochoudria*

The flavin content of tissues and tissue homogenates has been reported from time to time (see, for example, (l)), but quantitative information on the partition of flavins in more defined preparations used in the study of electron transport systems is generally meager (cj. (2)). Recently, Ziegler, Green, and Doeg (3) claimed that beef heart mitochondria contain only flavin adenine dinucleotide in the trichloroacetic acid-extractable fraction. However, the reduced diphosphopyridine nucleotide dehydrogenase (4) isolated from the snake venom digest of the Keilin-Hartree heart muscle preparation possesses riboflavin phosphate as the prosthetic group (5, 6).l I f the riboflavin phosphate of the dehydrogenase is not an artifact created during isolation, the heart muscle preparation should likewise contain pre-existing riboflavin phosphate. Indeed, we have detected this flavin in our preliminary experiments.2 The Keilin-Hartree preparation has been shown to be a preparation of disintegrated mitochondrial membrane (11)) and its behavior in nonphosphorylating respiration resembles (2) that of electron transport particles (10) and of intact mitochondria. These facts induced us to undertake a more extensive survey, based on a randomized block design, of the flavin distribution in the Keilin-Hartree preparation and in intact mitochondria. The results were further subjected to statistical analysis in order to reach objective conclusions, free from bias, from the experimental data. This paper describes the distribution of riboflavin phosphate, flavin adenine dinucleotide, and the acid-nonextract-