Effects of chronic infusion of dibutyryl c-AMP or adenosine on luteal function in sheep

Adenosine or vehicle; dibutyryl c-AMP, a c-AMP analogue, or vehicle in two separate experiments were infused through an indwelling cannula every four hours around the ovarian vascular pedicle of ewes unilaterally ovariectomized on day 8 postestrus. Adenosine or vehicle was infused from day 8 through 22 postestrus and dibutyryl-cAMP was infused from day 8 through 20 postestrus or until the ewes returned to estrus. Interestrous intervals were greater (p less than or equal to 0.05) in ewes receiving adenosine (27.3 +/- 2.4 days) than in control ewes (17.2 +/- 1.3 days). The length of the estrous cycle of ewes receiving dibutyryl c-AMP was greater (22.4 +/- 1.1; p less than or equal to 0.05) than in control ewes which averaged 16.7 +/- 0.6 days. Profiles of progesterone were different (p less than or equal to 0.05) for ewes receiving adenosine or dibutyryl c-AMP when compared to their respective controls. In addition, the overall mean concentrations of progesterone were greater (p less than or equal to 0.05) in dibutyryl c-AMP or adenosine-treated ewes than in controls. In a third experiment, infusions of adenosine or dibutyryl c-AMP intrauterine every 4 hours through a cannula from day 8 through 22 postestrus had no effect (p less than or equal to 0.05) on the interestrous interval or profiles of progesterone. It is concluded that dibutyryl c-AMP or adenosine in vivo can delay luteolysis and adenosine and c-AMP may play roles in luteal secretion of progesterone in sheep but are probably not the uterine embryonic antiluteolysin of early pregnancy in sheep.