Anaerobiosis in the Rana pipiens Embryo

BRACHET (1934,1950) has proposed that the oxidation source for the anaerobic development of the early amphibian embryo is primarily from a pool of materials such as oxidized glutathione. Inasmuch as an investigation of the defective lactate producing ability of hybrid embryos (Barth, 1946) was contemplated, it seemed desirable to reinvestigate the problem of the source of anaerobic oxidations in this embryo. This was particularly necessary since, as will be discussed later, amphibian embryos in normal development may always be partly anaerobic and reasonable alternate interpretations of Brachet's data were possible. Brachet's findings may be summarized briefly as showing (1) a production of carbon dioxide during anaerobiosis without diminution and indeed with some increase of tissue bicarbonates, and (2) a short burst of heightened oxygen uptake during return to oxygen with an R.Q. of about 0-3-0-5. The low R.Q. appeared to Brachet to rule out oxidation of lactate and he attributed this to the regeneration of an oxidizable reserve that had been reduced during anaerobiosis. It is conceivable, however, that in the presence of substantial amounts of lactate the turnover of lactate to pyruvate might be so rapid as to exceed any disposal of the pyruvate to carbon dioxide or other metabolites. This pyruvate formation involves necessarily the reduction of DPN. Accordingly, a good part of the oxygen uptake might be due to the reoxidation of DPN. Since such reoxidation is believed to involve the generation of high-energy phosphate bonds as ATP (Ochoa & Stern, 1952), this reoxidation would constitute a partial payment of the so-called 'oxygen debt' incurred during the utilization of fermentative degradation of glycogen. Since this reoxidation of DPN does not involve the production of carbon dioxide, a low R.Q. is to be expected. The gross outlines of the glycolytic system of Rana pipiens embryo have been described (Cohen, 1954) and lactic dehydrogenase activity is present. Accordingly the above hypothesis has a real basis and can be tested by concurrently following respiration and lactate disappearance during recovery from anaero-