Significance of serum early pregnancy factor concentrations during pregnancy and embryonic development in Sminthopsis macroura (Spencer) (Marsupialia: Dasyuridae)

Abstract

Marsupial pregnancy differs from that in eutherians in duration, placentation and hormonal profile so much so that maternal recognition of pregnancy may not occur in polyovular marsupials. However, a comparison of gravid and non-gravid uteri reveals differences indicative of histological and physiological adaptations to pregnancy. In the present study, the hypothesis that embryo-maternal signalling occurs in polyovular marsupials was tested by examining serum from non-pregnant and pregnant Sminthopsis macroura for the presence of early pregnancy factor (EPF), a serum protein secreted by the ovary in response to the presence of a newly fertilized egg in the oviduct. EPF is detectable in the serum of pregnant, but not in non-pregnant, females in all eutherians studied to date. In the present study, EPF was detected in S. macroura serum by the rosette inhibition test during the first 9 days of the 10.7 day gestation period in this marsupial. However, EPF was not detected on day 10, just before parturition, or in non-pregnant or preovulatory animals. Immunohistochemical analysis of ovaries from gravid and non-gravid animals demonstrates that EPF is found in the capillaries, interstitial spaces and secretory cells of the corpus luteum. It is concluded that the spatiotemporal pattern of EPF activity described strongly indicates that maternal recognition of pregnancy in marsupials is mediated, at least in part, by EPF. Because the endocrinological milieu is the same in pregnant and non-pregnant marsupials, the possibility of using marsupials as an experimental system for studying EPF function unconfounded by hormonal effects is presented.

Progesterone concentration in the marsupial Sminthopsis macroura: relationship with the conceptus, uterine glandular regeneration and body weight

“…Here, increased mitotic activity in the pregnant uterine epithelium of S. macroura, was coincident with the previously identified periods of elevated serum EPF (Cruz et al 2001), suggesting a possible relationship between EPF and uterine epithelial mitotic activity in S. macroura.…”

“…Early pregnancy factor (EPF), a protein detected in maternal serum, is found in S. macroura within 24 h of fertilization and is found at high levels between zygote uterine entry and unilaminar blastocyst formation (days 1-3), as well as immediately pre-implantation on day 8 (Cruz et al 2001). EPF is found in mice during these developmental stages, where it is required for zygote survival and cleavage, and it is also found during the peri-implantation period (Athanasas-Platsis et al 2000).…”

Investigation of the immunocompetent cells that bind early pregnancy factor and preliminary studies of the early pregnancy factor target molecule

“…EPF‐Fl‐mal solutions were stored at 4°C in the dark and used within 2 weeks of preparation. All preparations were tested in the rosette inhibition test in parallel with the unmodified synthetic molecule 26 , 27 , 28 ; EPF concentration was determined by double sandwich ELISA 29 . All manipulations involving Fl‐mal were performed under subdued lighting.…”

Early Pregnancy Diagnosis in Bovines: Current Status and Future Directions

“…EPF is reported to be present in the pregnant sera of most mammalian species including humans [56, 57], mice [51], sheep [58, 59], cows [60–62], pigs [63], mares [64], and some wild animals [65]. In buffalo pregnancy, Chander [66] demonstrated decreased E-rosette formation but failed to demonstrate the presence of a rosette inhibiting factor (RIF, which probably would have been EPF) in the serum.…”