In vitro effects of 13-cis-retinoic acid (Ro 4-3780) and etretinate (Ro 10-9359) on DNA synthesis and fine structure of guinea pig and human lymphoid cells.

In vitro effects of the retinoids 13-cis-retinoic acid (Ro4-3780) and etretinate (Ro 10-9359) on DNA synthesis and the fine structure of different guinea pig and human lymphoid cells were tested. 13-Cis-retinoic acid caused a dose-dependent inhibition of DNA synthesis most prominently in thymocytes. This effect was not due to an inhibition of thymidine uptake into the cells. Electron microscopically, the cells exhibited swollen Golgi cisternae, enlarged mitochondria often with condensed matrix, and an increased number of autophagic vacuoles. Etretinate, on the other hand, was without effect on DNA synthesis as well as on cell fine structure. The results suggest that the morphological and growth-inhibitory effects of 13-cis-retinoic acid are related.