RESPIRATORY REGULATION IN AMPHIBIAN DEVELOPMENT

Abstract

For Rana pipiens embryos, and gastrula-blocked Rana pipiens female X Rana sylvatica male embryos, the respiratory rate (potential) under maximal stimulation by 10-5[image] x 10-5[image] 2,4-dinitrophenol (DNP) is from 1.5 to 4 times greater than the respiratory rate (norm) under standard conditions. Current theories of DNP-action (cf. Ciba Foundation Symposium on the Regulation of Cell Metabolism, 1959) interpret this result as indicating that the respiratory norm is controlled by the rate of energy expenditure for morphogenesis. The exponentially increasing norms of normal embryos are thus due to increasing rates of energy-expenditure; the more slowly increasing norms of gastrula-blocked hybrids are explained similarly. The exponentially increasing potentials of normal embryos are ascribed to structural change facilitating enzyme-substrate union; a similar assumption accounts for the more slowly increasing potentials of hybrid embryos. Unaccounted for is the failure of DNP to elevate the respiratory rates of homogenized embryos, either normal or hybrid.