Fig. 9.

Effects of RA on the proliferation of epithelial supporting cells. Explants were cultured for 2 or 5 d in medium 199 and N2 and all-trans-retinoic acid (5 or 50 ng/ml). Inhibition of proliferation was observed in all RA-treated cultures. Treatment with RA did not, however, lead to increased numbers of calretinin⁺ hair cells (see Results).