Studies on biochemical characteristics of an early decidual protein.

Previous work in our laboratory has demonstrated the specific synthesis of a soluble protein (A) in the rat endometrium on day L4 of pseudopregnancy 1 h after the decidual induction; the A protein synthesis being higher in the antimesometrial region (AMR) than in the mesometrial one. We have now examined in the AMR of rat endometria on day L4 of pseudopregnancy: 1) the effect of cycloheximide (500 microgram, i.p. 30 min before decidual induction) on the biosynthesis of the A protein, and 2) the effect of actinomycin D (Act. D) (5 microgram/uterine horn 60 min before the decidual stimulation) on the induction of A protein synthesis. The synthesis of the A protein was determined by acrylamide gel electrophoresis of endometrial soluble proteins after double-labeling incorporation of amino acids. Results showed that: 1) the cycloheximide inhibited the synthesis of the A protein which indicates a de novo protein synthesis; 2) the Act. D inhibited the A synthesis suggesting that synthesis of an Act. D-sensitive product is one of the earliest macromolecular synthetic events after decidual induction.