Abstract
To investigate a possible role of retinoic acid (RA) as a morphogen, effect of treating embryonal carcinoma F9 with RA was analysed in detail. Differentiation of F9, as monitored by the secretion of basement membrane proteins, was biphasic depending on the dose of RA. Similar biphasic response was observed in the secretion of tissue type plasminogen activator. The biphasic pattern of differentiation was stable for long period, but dibutyryl cAMP changed it to monophasic after 12 days. Result of monitoring of laminin secretion 5 days after pulse treatment with RA for less than 12 h caused intermediate differentiation. For full differentiation, more than 24 h of pulse treatment was needed. This intermediate differentiation could be nullified only by washing twice with interval between. A plausible explanation for this result was that RA metabolite secreted by F9 is important for the differentiation.
