Effects of elevated levels of cyclic AMP on the embryonic chick mandible in vitro.

Mandibles were cultured in the presence of dibutyryl cyclic AMP (1 mM) and theophylline (1 mM) and in control medium. Controls differentiated normally but the timing of events differed from that in ovo and feathers did not form. With elevated intracellular cyclic-AMP levels, membrane bone did not form in the earlier stages tested and was inhibited or reduced in older ones; chondrogenesis was inhibited only in young explants (HH stage 20) and, in certain instances, it was enhanced. There was precocious and hyperplastic differentiation of mucous cells within oral epithelium but the aboral epithelium was unchanged.