Indispensability of Iron-bound Chick Transferrin for Chick Myogenesis in Vitro. (myogenesis/transfrrin/iron)

Abstract

Myotropic activity of highly purified chick transferrins (Tf) to chick primary myogenic cells was studied in a culture medium containing horse serum. Fe-binding to Tf is indispensable for the activity. The removal of Fe from Tf gives rise to a complete loss of the activity, and it is restored by Fe-rebinding depending on the amount of bound Fe. This result, combined with other physicochemical and immunological data, strongly confirms that the myotropic activity is exerted by the Tf themselves, not by a contaminating material(s). Culture medium containing horse Tf which seems inadequate for the study of the biological effects of Tf is suitable for studies on chick Tf, since horse Tf is inactive in promoting chick myogenesis. Terminal sialic acid residues are unrelated to myotropic activity since Tf with different numbers of residues (0, 1, and 2 mol/Tf molecule) are comparable in their activies. The mechanism of Tf action on cells and contradictions among previous papers as the requirement of Tf for cell growth were discussed from the viewpoint of an Fe donor with class-specificity.