Effects of progesterone on labeling of soluble proteins and glycoproteins in rabbit endometrium

An in vitro test system was used to study in vivo effects of progesterone on synthesis and secretion of total proteins and glycoproteins in rabbit endometrium. Endometrial explants incubated in Eagle's minimal essential medium containing radioactive leucine and N-acetylglucosamine were found to synthesize soluble proteins readily, including glycoproteins. Furthermore, significant amounts of newly synthesized proteins, including blastokinin, were released by the tissues into the incubation medium. In addition, in vitro synthesis and release of labeled proteins by estrogen-primed endometrial tissue (E-primed tissue) was significantly enhanced by exposure of the tissues to progesterone in vivo. Double-labeling studies demonstrated qualitative as well as quantitative differences in peptide synthesis between E-primed tissues and E-primed, progesterone-treated tissues. Progesterone also stimulated both the synthesis and the release of glycoprotein by E-primed tissues. These studies, therefore, suggest that progesterone regulates qualitatively and quantitatively the synthesis and secretion of total proteins, including glyco-proteins, in rabbit endometrium.