Abstract
Experiments were conducted to study the stimulus
for PGF„ release from the uterus and the utero-ovarian
2oc
pathway for PGF2oc transport in sheep
Frequent uterine venous blood samples were
collected from the mammary vein after anastomosing it
with the uterine rein, while simultaneous uterine tissue
samples were obtained by fistulation of the uterine horn
through the abdominal wall thus exposing the uterine
endometrium to the exterior. Uterine venous blood and
tissue samples were analysed for PGF2cC» progesterone and
oestradioi-17/3 and endometrial PGF~ and PGE~ content '
2oc 2
and synthesizing ability respectively. There was an
increase in PGF_ release towards the end of the cycle 2oc
with peaks appearing consistently at 30-45 and 3-9 hrs
before the decline in progesterone conc^trations.
Further PGF^ peaks occurred after the initiation of
progesterone decline in 4 of 5 cycles studied. Elevation
of endometrial PGF_ content and synthesizing ability Zee
occurred at similar times to PGF„ release, but did not 2oc
consistently either precede, coincide or follow it. This
suggested that neither an increase in PGF2oC content or
an increase in the ability of the uterus to synthesize
PGF2qc are prerequsites for PGF2oC release. Oestradiol-17^3
showed an increase in levels around the time of both
periods of PGF2qc increase. These elevated levels of
oestradiol-17/3 precede and/or coincide with peaks of
PGF2oc , thus confirming a role for oestradiol in PG^oc
release. An increase in oestradiol-17/3' and PGF„ was
zoc
also observed after the commencement of progesterone
decline but before oestrus.
Investigations into the utero-ovarian pathway for
PGF2oc imitated that the oestr°us cycle of the ewes were
extended when the uterine vein was cannulated and all
otner direct tissue connections between the uterine horn
and the ipsilateral ovary were surgically separated. The
results demonstrated that blood passing through the
uterine vein is not sufficient to account for the
luteolytic effect of the uterus on the ipsilateral ovary .
Examination of the anatomy of the uterine lymphatic
drainage revealed that there was no direct lymph flow
between the uterus and ovaries, and that the main
uterine lymphatic trunks were in close association with
the main utero-ovarian artery. In view of this finding
the availability of prostaglandins in lymph drainage
from the uterus at different stages of the oestr°us cycle
was examined. Samples of uterine lymph were collected on
different days of the oestr°us cycle and analysis showed
that PGF2qc was present in this lymph in amounts
comparable to those in uterine venous blood.
Furthermore, the mean concentration remained low until
day 12, while increased amounts were present from day 12
onwards. There was no significant variation in PGE2 in
o
uterine lymph during the oestrus cycle. Sequential
uterine lymph samples were obtained by chronic
cannulacion of a uterine lyrnpn vessel. These sequential
samples were analysed for PGF^^, PGE2' Pro<3esterone anc^
oestradiol-17/3 . The results indicated that the
concentration of PGF2qc in uterine lymph fluctuated
considerably, with a complex series of peaks being
apparent especially from the time of initiation of
luteal regression (day 12) to the end of the cycle. The
results demonstrated that PGF2(X is present in uterine
lymph in increased quantities at the time of luteal
regression. Again there was no significant change in
PGE2 concentration. However there were high levels of
oestradiol-17/3 / and progesterone levels did not decline
to low levels that were seen in venous blood. It was
transfer system similar to that propose! for tna
concluded that, it is possible that a counter-current^
transfer of PGF„ from the utero-ovarian vein to the
2oc
ovarian artery may occur between the main uterine lymph
trunks and the ovarian arterial blood, and so form an
additional or even alternative method of transfer of
PGF2oc from the uterus to the ovary.
