PURINE MODULATION OF PROSTAGLANDIN-F2-ALPHA (PGF2-ALPHA)-INDUCED PREMATURE LUTEOLYSIS INVIVO IN NONPREGNANT SHEEP

In two separate experiments, control and PGF2-alpha-treated unilaterally ovariectomized ewes received vehicle or adenosine every four hours through an exteriorized catheter installed either to parafuse the ovarian vascular pedicle of the remaining ovary containing a corpus luteum (CL) or to infuse intrauterine ipsilateral to the remaining ovary with the CL. Infusions were given every four hours from day 7 through day 22 postestrus or until ewes returned to estrus. Chronic infusion of vehicle intrauterine or parafusion of the ovarian vascular pedicle with vehicle in PGF2-alpha-treated ewes shortened the interestrous interval compared to controls (P less-than-or-equal-to 0.05). However, chronic parafusion of the ovarian vascular pedicle with adenosine in PGF2-alpha-treated ewes prevented a PGF2-alpha-induced premature luteolysis (P less-than-or-equal-to 0.05) but not when adenosine was infused chronically intrauterine (P greater-than-or-equal-to 0.05). It is concluded that adenosine can block a PGF2-alpha-induced premature luteolysis in vivo and may have roles in regulation of luteal secretion of progesterone but it is probably not the embryonic antiluteolysin of early pregnancy in ewes.