Glucocorticoid induction of egg white mRNAs in chick oviduct.

Glucocorticoids induce ovalbumin and conalbumin mRNA in oviducts from chicks withdrawn from prior estrogen treatment. The magnitude and the kinetics of the responses obtained, either in vivo or in vitro, are comparable to those obtained with estrogen or progesterone. With cultured oviducts, 1 nM dexamethasone is sufficient for half-maximal accumulation of nuclear receptors and partial induction of both mRNAs, while maximal levels of receptors and both mRNAs are achieved with 30 to 100 nM dexamethasone. Competition experiments show that dexamethasone acts by binding to a class of high affinity receptors distinct from the sex steroid receptors. Dexamethasone acts synergistically with estrogen, but not with progesterone.