AJP - Endocrinology and Metabolism, Vol 241, Issue 2 142-E145, Copyright © 1981 by American Physiological Society
Uterine blood flow and timing of blastocyst implantation in the guinea pig
D. R. Garris and D. S. Whitehead
The temporal and direct relationships between serum estradiol (E) and
progesterone (P) levels and uterine blood flow (UBF) and intrauterine
oxygen tension (IU PO2) were examined in guinea pigs between days 1 and 8
of pregnancy. Both UBF and IU PO2 were measured in situ using a noninvasive
electromagnetic blood flow monitor and needle oxygen electrode,
respectively. Serum P levels remained relatively constant throughout the
first 8 days of pregnancy. In contrast, serum E levels declined to basal
levels between days 1 and 3, and then subsequently rose between days 4 and
7 before again falling to basal levels by day 8. The changes in UBF and IU
PO2 paralleled those of serum E levels, both exhibiting a rise between days
5 and 6. The direct effect of oil, E, or P injections on UBF and IU PO2
measurements in ovariectomized animals indicated that E induced a dramatic
rise in both uterine parameters, whereas both measurements remained at
basal levels after oil or P treatment. The results of this study indicate
that UBF and IU PO2 levels are directly regulated by the cyclic
fluctuations in serum E. The temporal relationship between the days 4 to 7
rise in serum E, UBF, and IU PO2 levels and the timing of blastocyst
implantation suggest that these events are involved in uterine preparation
for nidation in the guinea pig.
