Prostaglandin F Concentration in the Utero—ovarian Venous Plasma of the Ewe During the Oestrous Cycle

Abstract

Prostaglandin F2\ g=a\ . (PGF2\g=a\) is luteolytic in the ewe when infused into the ovarian artery (Barrett, Blockey, Brown, Cumming, Goding, Mole & Obst, 1971; McCracken, Baird & Goding, 1971) or the ipsilateral uterine vein (Thorburn & Nicol, 1971). These observations, together with the identification of PGF2\g=a\ in the uterine venous plasma of anaesthetized ewes towards the end of the oestrous cycle (Bland, Horton & Poyser, 1971;McCracken et al. 1971), strongly suggest that PGF2\g=a\ is the uterine luteolytic factor in sheep. This paper describes in detail the changes in PGF concentration in utero\p=m-\ovarian venous plasma of conscious ewes during the oestrous cycle.Polyvinyl catheters (1\m=.\5 mm o.d.) were inserted into the right and left utero\p=m-\ ovarian veins via uterine vein branches in two Merino ewes 10 and 11 days after oestrus. Utero\p=m-\ovarian venous samples were collected every 2-3 h from the day after surgery.Concentrations of PGF were measured by a radioimmunoassay (Thorburn, Nicol, Bassett, Shutt & Cox, 1972) using antisera raised in rabbits. Prostaglandin F2a and PGFloe compete in an almost identical manner with [9-3H]PGF2lx over the analytical range (0-1-3-0 ng) of the assay. Prostaglandin E2 competes only weakly and no crossreaction was observed with a wide range of steroids and lipids tested. Plasma samples (0-5 ml) were extracted with chloroform, then acidified and re-extracted. The second chloroform extracts were chromatographed on silica gel columns to separate the PGF group from other prostaglandins. Method blanks were equivalent to 0-2 ng PGF and recoveries averaged 60%. Identity of the measured substances as PGF or PGF-like compounds was based on the selective extraction procedure, Chromatographie puri¬ fication and the specificity of the antibodies to PGF ; also negligible values were ob¬ tained with peripheral plasma. Data were corrected for blank values and procedural losses. Progesterone was measured by the method of Thorburn & Schneider (1972).With frequent sampling we detected a complex series of peaks in the concentration of PGF between days 13 and 17 of the oestrous cycle (Fig. 1). These peaks were of short duration and increased in frequency as oestrus approached. Very low concen¬ trations were measured at other times except on days 2 and 3 in samples from one ewe (3976). In this same ewe, which had a corpus luteum (CL) in each ovary, there was striking similarity in the concentrations of PGF on each side (Fig. 1). Ewe 4854 had a single CL in the right ovary during the first cycle.

ENHANCED INACTIVATION OF PROSTAGLANDIN E2 BY THE RABBIT LUNG DURING PREGNANCY OR PROGESTERONE TREATMENT

“…Discussion pregnant ig prostaThese experiments show that the capacity of the k-pregnant rabbit lung to inactivate prostaglandin E2 increases pregnant during pregnancy. Most of our evidence was reaction obtained from in vivo experiments because we (Thorburn, Cox, Currie, Restall & Schneider, 1972). A difficulty was encountered in that the dose-response curves measured in these experiments were not parallel, those for the intravenous injections being steeper than those for the intra-arterial injections.…”

Additional pathway of transfer of uterine prostaglandin F-2 to the ovary in sheep

“…The quantity incor¬ porated into each assay for calculating this value was 160 pg PGF-2a. The (Thorburn, Cox, Currie, Restall & Schneider, 1973). These results suggest that PGF-2a can also reach the ovary via the venous drainage passing alongside the oviduct.…”

Regulation of Interferon-.TAU. Gene Expression and the Maternal Recognition of Pregnancy.

“…Processes of luteal regression are characterized by a loss of progesterone production (functional regression) and tissue demise such as physiological cell death and apoptosis (structural regression) [3]. In sheep, endometrial production of PGF 2α begins secretion in a pulsatile manner on day 12 of the estrous cycle, but its synthesis and/or secretion is attenuated if pregnancy is established [4,5]. It has been thought that a signal(s), which causes the attenuation of endometrial PGF2α production, is produced by the conceptus, resulting in the inhibition of luteal regression.…”