Synergistic Effects of Oestrogen and Progesterone on Ovomucoid and Conalbumin mRNA Synthesis in Chick Oviduct

Abstract

OESTROGEN, progesterone and testosterone regulate the cytodifferentiation of the tubular gland cells which synthesise the majority of the egg white proteins and modulate specific protein synthesis^1–6. Once tubular gland cells have differentiated in the presence of oestrogen, the synthesis of the egg white proteins can be induced by either oestrogen or progesterone^{3, 6}. We reported that the synthesis of two of these proteins, conalbumin and ovomucoid, is maximally stimulated only with combinations of oestrogen and progesterone⁶. The evidence suggested that these effects were synergistic rather than simply additive. In order to answer the question of whether these synergistic effects were at the level of mRNA translation or mRNA synthesis, we isolated and quantified the messengers for these proteins by assaying them in a protein-synthesising system derived from rabbit reticulocytes⁷. Here we show directly that the different rates of specific protein synthesis reflect different mRNA concentrations.