The transition from tadpole to frog haemoglobin during natural amphibian metamorphosis. I. Protein synthesis by peripheral blood cells in vitro.

The transition from larval to adult haemoglobin during natural metamorphosis of Rana catesbeiana tadpoles was studied by polyacrylamide gel electrophoresis of either untreated or reduced and alkylated haemolysates in 8 M urea. The capacity of the peripheral red cells to synthesize haemoglobin in vitro declined in the course of the development of tadpoles prior to metamorphosis. The beginning of the metamorphosis climax, characterized by emergence of the front legs, was associated with an abrupt increase in the capacity of the circulating cells to synthesize haemoglobin. The protein synthesized at this stage consisted mainly of frog haemoglobin and of smaller amounts of tadpole haemoglobin. The observed changes in haemoglobin synthesis during metamorphosis are compatible either with the appearance of a new cell line synthesizing adult haemoglobin, or with the renewed proliferation of the tadpole erythroid cell line which eventually produces cells capable of synthesis of frog haemoglobin.