Flavin compound in frog eye.

In 1934, Euler and Adler (1) recognized that a large amount of flavin compound was contained in retina of certain fishes and all of it was dialysable through collodium membrane, and stated that the fluorescence of flavin compound in the retina might have some connection with visual senses. Karrer and Fritsche (2), by their fluorescence-gauging curve of flavin compound, considered that the fluorescence of flavin compound in the retina intensified the visual senses. Brunner and Baroni (3) found that the absorption spectrum of the flavin compound contained in the retina corresponeded to that of lactflavin, and that by cataphoresis this flavin compound was not found to be an ester of phosphoric acid. Euler and Adler (4) reexamined this problem using benzyl alcohol and emphasized that the flavin compound in the retina is free riboflavin, and not an ester of phosphoric acid. Consequently it does not take part in the respiration of the retina but in the visual action because of its fluorescence. Siillmann (5) found that flavin compound accelerated the oxidation of pyruvic acid in the retina, but he did not mention any enzymatic action, believing that flavin compound acted only optically. On the other hand, Nakashima (6) and Kubowitz (7) clearly demonstrated that the retina conducted an exeedingly vigorous respiration. Fleischmann et al. (8) reported that the flavin compound had a favourable influence on the respiration of the retina of rabbits inhibited by cyanic acid. It seems therefore quite possible, in spite of the opinions of the above mentioned investigators, that the flavin compound acts as co-enzymes in the retina. From this point of view, experiments were made to determine the significance of its flavin compound. As a first step, an attempt was made to investigate (a) the distribution of flavin compound.in the eyes, (b) its change at different seasons, (c) the attitude of flavin compound when the eye is exposed to light, and (d) in what condition this flavin compound exists in the retina. In regard to the distribution of flavin compound in the eye, investigations were made by Manabe (9), Takada and Nagamura (10) on various animals and cod-fish, but concerning frogs, Manabe has reported only on some cases of toads (Bufo vulgaris formosus).