Embryonic diapause in European roe deer (Capreolus capreolus)
The total gestation period in the roe deer is approximately 290 days (10 months). When the blastocyst reaches the 20-30 stage it enters a 5-month period of diapause. During the last six weeks of diapause the blastocyst undergoes mitosis and reactivates in late December or early January at the 100-cell stage. The conceptus undergoes a period of rapid growth, which lasts between 7 and 25 days, before attachment to the endometrium and normal fetal growth. By studying the period between late diapause and early fetal development, it was possible to monitor changes in the reproductively important hormones, progesterone, oestradiol-17β, prolactin and pregnancy-associated glycoproteins as well as the secretion of important signalling proteins by the conceptus and uterus. In addition, investigations were undertaken to determine whether a regimen of long day photoperiod manipulation would effect the duration of diapause. Both peripheral concentrations and luteal release of progesterone remained consistent throughout diapause, reactivation and implantation (peripheral progesterone: 3.82 ± 1.97 ng ml-1; luteal progesterone: 6.72 ± 0.81 ng mg-1 protein). Oestradiol concentrations remained low during diapause (1.07 ± 0.4 pg ml-1) and expansion (1.2 ± 0.4 pg ml-1) but increased 30 times at trophoblast elongation (49.17 ± 0.37 pg ml-1) but increased 30 times at trophoblast elongation (49.17 ± 0.37 pg ml-1). Both prolactin and pregnancy-associated glycoproteins remained at basal concentrations (4.69 ± 0.86 pg ml-1 and <4.5 ng-ml-1 respectively) and increased after implantation (12.34 ± 2.71 ng ml-1 and 7.74 ± 0.47 ng ml-1 respectively). Incorporation of a radiolabel into conceptus secretory proteins increased four times at expansion compared with diapause, whereas incorporation into endometrial secretions remained constant. At elongation, incorporation into endometrial secretions increased two times and conceptus secretions increased 32 times. Endometrial secretions remained at these levels until implantation when they decreased linearly as fetal development progressed. Two-dimensional electrophoresis and fluorography showed that the profile of endometrial secretory proteins was constant until implantation when qualitative changes were evident.