Changes in galactosyltransferase activity in chick pectoral muscle during embryonic development

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Abstract
The 2 major vertebrate galactosyltransferases were investigated in developing chick muscle in ovo and in vitro, and in cultured chick fibroblasts. The 2 enzymes were UDP-galactose-N-acetylglucosamine galactosyltransferase (galactosyltransferase I; EC 2.4.1.22) and UDP-galactose-N-acetylgalactosamine galactosyltransferase (galactosyltransferase II). Both activities fell during muscle development in ovo. Galactosyltransferase I activity was constant from day 7-16, after which it declined 5-fold; galactosyltransferase II activity fell markedly from day 9-13 and 16-20, displaying an overall 8-fold decrease. In primary muscle cultures galactosyltransferase I activity fell slightly during 7 days in culture; galactosyltransferase II increased 2-fold during the same period. No significant change in activity of either galactosyltransferase was observed during intercellular recognition and fusion. Analysis of muscle cultures treated with cytosine arabinoside and of fibroblast cultures revealed that the majority of galactosyltransferase I activity in primary muscle cultures is associated with fibroblasts; the majority of galactosyltransferase II activity is muscle-associated. The addition of 5-bromodeoxyuridine to primary muscle cultures resulted in a 3-fold rise in activities of both transferases.