Temporal changes in reproductive hormones and conceptus-endometrial interactions during embryonic diapause and reactivation of the blastocyst in European roe deer (Capreolus capreolus)

The roe deer blastocyst is in diapause between August and December, after w hich time it expands and elongates rapidly before implantation. Blood sampl es were taken from 30 animals to define temporal changes in reproductively important hormones to investigate the physiological cues present at embryo reactivation. In 15 of these animals, changes in uterine and conceptus prot ein synthesis and secretion, and luteal progesterone release during diapaus e and reactivation, were assessed after culture of these tissues in vitro. Oestradiol concentrations remained low during diapause (1.07 +/- 0.4 pg ml( -1)) and expansion (1.2 +/- 0.4 pg ml(-1)) but increased by 30 times at tro phoblast elongation (49.17 +/- 0.37 pg ml(-1)). Prolactin remained at basal concentrations (4.69 +/- 0.86 ng ml(-1)) and increased after implantation (12.34 +/- 2.71 ng ml(-1)). Peripheral progesterone concentrations and lute al progesterone release remained constant throughout diapause, reactivation and implantation (peripheral progesterone: 3.82 +/- 1.97 ng ml(-1); luteal progesterone: 6.72 +/- 0.81 ng mg(-1) protein). Incorporation of a radiola bel into conceptus secretory proteins increased by four times at expansion compared with diapause, whereas incorporation into endometrial secretions r emained constant. At elongation, incorporation into endometrial secretions increased two times and conceptus secretions increased 32 times. Two-dimens ional electrophoresis and fluorography showed that the profile of endometri al secretory proteins was constant until implantation when qualitative chan ges were evident. Although a role for an endocrine maternal trigger of reac tivation from diapause cannot be dismissed, these data provide no supportin g evidence and indicate that the conceptus itself may drive reactivation.