ABSTRACT
In this chapter, the authors show that Drosophila cells of several clones derived from in vitro-established lines were target cells for ecdysterone, a steroid hormone controlling differentiation and development in insects. They examine the energetic cost of cellular differentiation and the relationships between the cellular differentiation and the aerobic metabolism of the cells. In the case of ecdysterone action, the increase of toxic products is balanced by an increased induction of the enzymatic defenses. The cells avoid the danger of the consequent overproduction of products of O2 reduction by an increased activity of the defense enzymes superoxide dismutase and catalase. The rate of synthesis of actin was scarcely increased by ecdysterone when the gas phase was nitrogen whereas the synthesis was greatly enhanced in good oxygenation conditions. The criteria of differentiation retained were the induction of enzymatic activities and the increase of the rate of synthesis of actin by ecdysterone.
