[Studies of the activity and the isoenzyme patterns of LDH during the development ofXenopus laevis, Triturus alpestris andvulgaris andAmbystoma mexicanum].

The present paper deals with studies of the activity and the isoenzyme patterns of LDH during the development ofXenopus laevis, Triturus alpestris andvulgaris andAmbystoma mexicanum. Activity measurements have been performed with the optical test method using pyruvate as substrate and the isoenzymes have been separated by vertical starch gel electrophoresis. a) Substrate optima for enzyme extracts from embryonic stages 1-38 are identical in the three speciesTriturus alpestris, Ambystoma mexicanum andXenopus laevis and lie in the range of 1.2-1.4 mM pyruvate. b) Uncleaved eggs ofXenopus andTriturus alpestris contain almost the same activities of LDH/embryo, whereas the eggs ofAmbystoma show values twice as high. The activity per embryo is fairly constant between stage 1 and 26 in all species tested. Only a slight rise takes place during gastrulation and neurulation, but a second increase becomes pronounced after the embryos have reached stage 30. c) The activity of LDH, LDH per mg soluble protein in embryonic extracts rises during gastrulation and neurulation inTriturus alpestris, Ambystoma mexicanum andXenopus laevis compared to the uncleaved egg. After having fallen to a minimum at stage 26, it rises again inTriturus alpestris andXenopus embryos and approaches a limiting value after stage 40. InAmbystoma however the LDH activity mg soluble protein decreases after stage 26 and approaches the same limiting value as inTriturus alpestris andXenopus, so that the marked difference in activity values between uncleaved eggs ofAmbystoma on the one hand andTriturus alpestris andXenopus on the other hand diminishes considerably after stage 40. d) During early embryonic development the isoenzyme pattern of LDH is rather constant in all four species tested and is species-specific. With the onset of organogenesis, especially when the myotomes begin to function (stage 26), basic isoenzymes, which are dominant in adult skeletal muscle and other adult organs, appear for the first time inXenopus, Triturus alpestris andT. vulgaris. Neither quantitative nor qualitative changes are detectable in the isoenzyme pattern ofAmbystoma during development until stage 40; the general pattern of adult tissues exists here already in the egg.