Physiological aspects of blastocyst uterine interaction.
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Date
1984-07
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Abstract
An interaction between the blastocyst and the uterus is essential for establishment
of pregnancy. Because maternal estrogen is not an absolute requirement, estrogen of
embryonic origin has been implicated in this process in the pig and the rabbit. Furthermore,
estrogen forming capacity has been documented in the blastocyst of these species. However,
while the complete machinery for steroid synthesis in the pig balstocyst has been demonstrated,
the issue is still unresolved for the rabbit blastocyst. In the present communication
we have shown that 17α-hydroxylase and C17-20-lyase, enzymes involved in the formation of
androgens (C19-steroids) from C21-steroids (progestins), are present in day-6 rabbit blastocysts.
C17-20-lyase activity was undetectable to low in day-5 and increased in day-6 balstocysts.
The activity was further increased in day-6 blastocysts cultured for 24 h. Because prostaglandins
have been implicated in uterine vascular changes at about the time of implantation
and pregnancy establishment, and because catechol estrogens are more potent than phenolic
estrogens in stimulating prostaglandin synthesis in the blastocyst and the uterus, we
determined catechol estrogen forming capacity in the rabbit and pig blastocyst. Catechol
estrogen forming capacity (estrogen-2/4-hydroxylase) in the pig blastocyst appears on day 10
of pregnancy, peaks on day 12 and then declines. Our preliminary experiments also indicate
that day-6 rabbit blastocysts have catechol estrogen forming capacity. On the basis of our
present findings and of others, we propose that catechol estrogens of embryonic origin mediate
the stimulatory effect of estrogens on prostaglandin synthesis in the embryo and/or the uterus
and thus participate in the process of establishment of pregnancy.
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Keywords
Blastocysts, implantation, pregnancy recognition, catecholestrogens, prostaglandins, aromatase
Citation
Dey S K, Davis D L, Hersey R M, Weisz Judith, Johnson D C, Pakrasi P L. Physiological aspects of blastocyst uterine interaction. Journal of Biosciences. 1984 July; 6(suppl_2): s23-s31.