ATP level and respiration of embryos.

A considerable increase in the rate of oxygen consumption is known to occur during the development of embryos (cf. Needham, 1931; Tuft, 1953; Brachet, 1960; Gustafson, 1965). However, the mechanism of the increase in respiration during embryonic development is still unclear. A certain correlation seems to exist between DNA synthesis and the respiration of embryos (Comita & Whiteleley, 1953; Brachet, 1960). According to Commoner (1964), this correlation is determined by a change in the level of free nucleotides in cells when the rate of DNA synthesis changes. Free nucleotides control cell metabolism, oxidative processes in particular. The ADP+P/ATP ratio is known to control the rate and direction of electron transfer in the respiratory chain (Chance & Hagihara, 1961; Klingenberg & Schollmeyer, 1961). The ADP/ATP system is suggested to control the rate of oxidative metabolism in fertilization (Monroy, 1965 a, b; Zotin, Milman & Faustov, 1967). The work described below was aimed at the elucidation of the role played by ATP in respiration changes of embryos during their development and during changes in environmental temperature.