Thymidine kinase, thymidilate kinase and thymidilate synthetase activities have been studied during differentation in culture of muscle cells from chick embryo both in dplicating myoblasts and in post-mitotic myotubes. Thymidine kinase activity starts decreasing long before fusion, when myoblasts are still actively engaged in DNA synthesis and it reaches a minimum value at fusion (approx. 70 h of culture). Also thymidilate synthetase undergoes a precocious alteration of its activity which is low at 24 h culture, it increases up to 48 h and drops to a very low level after fusion. Finally, thymidilate kinase activity remains constant during the duplicative period and declines only after fusion. Pulse-labelling experiments with [3H]thymidine and [3H]deoxycytidine show that the incorporation of these precursors into the deoxynucleotide pool and into DNA parallels the patterns of the enzymatic activities measured in vitro.
ASJC Scopus subject areas
- Developmental Biology