[Electron microscopic study of the effects of thyroxine and exogenous RNA on cultured cells]

Dependence of thyroxin effect on the level of transcription and the influence of exogenous RNA synthesized by injection of thyroxin to animals was studied in culture cells electron microscopically. Thyroxin was stated to produce changes in nuclear structures, the development of endoplasmic network, increase in number of ribosomes, hypertrophy of the laminar complex. A partial blockade of transcription by actinomycine prevents the manifestation of thyroxin effect on the state of cell ultrastructures. Injection of RNA obtained from organs of rats treated with thyroxin to some extent imitates thyroxin action on the state of protein-synthesizing of the cell. The data were presented on the existance of some genetic link in the mechanism of thyroxin action affecting ultrastructural organization of the cell.