VITAMIN-A IS INVOLVED IN ESTROGEN-INDUCED CELL-PROLIFERATION BUT NOT IN CYTODIFFERENTIATION OF THE CHICKEN OVIDUCT

We examined vitamin A-deficient chicks to determine whether vitamin A affects the estrogen-induced development of the chick oviduct. When ov iduct development was stimulated for 5 days with the synthetic estroge n, diethylstilbestrol, the wet weight of the oviduct in vitamin A-defi cient chicks was only half that in control chicks. The DNA content in this tissue showed that the decreased oviduct weight in the vitamin A- deficient chicks was caused by the decreased proliferation of oviduct cells. However, the estrogen-induced expression of the ovalbumin gene was not affected by the vitamin A deficiency, suggesting that estrogen -induced cytodifferentiation is not affected by vitamin A. To clarify the vitamin A action on estrogen-induced development in the oviduct, t ranscripts of nuclear estrogen receptor (ER) and all-trans-retinoic ac id (RAR alpha, beta and gamma) receptors, which exert the effects of e strogen and vitamin A, were measured. The ER, RAR alpha: and RAR beta genes, but not that of RAR gamma, were expressed during oviduct develo pment, indicating that estrogen and vitamin A may control the expressi on of target genes through their cognate receptors. Thus, we have show n that vitamin A is involved in estrogen-induced cell proliferation bu t not in cytodifferentiation of the chicken oviduct.