Effects of Actinomycin D on the Lens Regenerating System.

A U T O R A D I O G R A P H I C studies of transformation of iris into lens during Wolffian lens regeneration of adult Triturus viridescens indicate an enhancement of RNA synthesis in the nucleus of the iris cells in the early phase of regeneration (Yamada & Karasaki, 1963; unpublished). Activation of protein synthesis and production of lens antigens follow the enhancement of RNA synthesis (Yamada & Takata, 1963; Takata et al, 1964). This sequence of events suggests the possibility that lens removal elicits synthesis of specific RNA's which in their turn induce synthesis of proteins essential for transformation of the tissue. If this is the case, it should be possible to suppress lens regeneration by subjecting the system to an inhibitor of RNA synthesis. In the present study the possibility was tested, using actinomycin D as the inhibitor. This antibiotic has been shown to be a specific inhibitor of RNA synthesis dependent upon DNA as the primer (Goldberg et al, 1962; Hurwitz et al, 1962; Reich et al, 1962), and to interfere with morphogenesis of various developmental systems (Brachet & Denis, 1963; Flickinger, 1963; Gross & Cousineau, 1963; Lallier, 1963; Markman & Runnstrom, 1963; Pierro, 1962; Wallace & Elsdale, 1963). In our experiments actinomycin was injected into the body cavity of adult T. viridescens, in which the tissue transformation had been initiated by lens removal. The effects of such treatment on the tissue transformation were studied in serial sections of the regenerates. By adjusting experimental conditions, it was possible to suppress lens formation or to demonstrate differential susceptibility in various cell types which are undergoing differentiation.