Effect of vitamin A acid on the growth of keratinocytes in culture.

The effect of vitamin A acid on the culture of guinea pig ear keratinocytes was investigated. Use of this agent and treatment of the plastic dishes with collagen solution facilitated attachment and growth. Vitamin A acid elicited a wave of DNA synthesis which was studied by incorporation of tritiated thymidine and quantitation of cellular DNA, particularly during the period 24--45 h after plating. During this period, thymidine incorporation into DNA was increased ten-fold by vitamin A acid and showed a complex pattern of peaks and shoulders which may represent the S phase of synchronous keratinocytes.