Stimulation of 2′,5′-oligoadenylate synthetase activity in sheep endometrium during pregnancy, by intrauterine infusion of ovine trophoblast protein-1, and by intramuscular administration of recombinant bovine interferon-αI1

Summary. In Expt 1, activity of 2′,5′-oligoadenylate (2′,5′-A) synthetase in endometrium collected on Day 16 (oestrus is Day 0) from the uterine horn ipsilateral to the corpus luteum was greater (P < 0·001) for pregnant (135·5 ± 1·72 nmol/mg protein/h) than for cyclic ewes (58·5 ± 0·99 nmol/mg protein/h). In pregnant ewes, activity of 2′,5′-A synthetase in endometrium collected from the contralateral uterine horn(119·5 ± 1·72nmol/mg protein/h) did not differ from that of the ipsilateral horn. In Expt 2, three ovariectomized ewes were treated with progesterone for 10 days and then with oestrogen for 2 days. Activity of 2′,5′-A synthetase on Day 13 was 18% greater (P < 0·10) in endometrium collected from the uterine horn receiving infusions of 30 μg ovine trophoblast protein-1 (oTP-1) twice a day on Days 10,11 and 12(57·7 ± 0·22 nmol/mg protein/h) than from the uterine horn receiving control infusions of serum protein (SP; 48·8 ± 0·22 nmol/mg protein/h). In Expt 3, activity of 2′,5′-A synthetase on Day 15 was not significantly greater in endometrium collected from the uterine horn of cyclic ewes receiving infusions of 30 μg oTP-1 twice a day on Days 12, 13 and 14 (46·5 ± 0·37 nmol/mg protein/h) than in endometrium from the uterine horn receiving infusions of SP (38·2 ± 0·37 nmol/mg protein/h). When results of Expt 2 and Expt 3 were combined, intrauterine infusion of oTP-1 increased (P < 0·05) activity of 2′,5′-A synthetase in endometrium by 20%. In Expt 4, activity of 2′,5′-A synthetase in endometrium collected from cyclic ewes on Day 16 was increased (P < 0·001)by i.m.injection of 1 mg recombinant bovine interferon-αI1 twice a day on Days 12, 13, 14 and 15 (993·8 ± 85·9 nmol/mg protein/h) compared with endometrium from ewes similarly treated with placebo (162·1 ± 85·9 nmol/mg protein/h). These results indicate that activity of 2′,5′-A synthetase in endometrium of ewes was increased during early pregnancy, probably by the action of the antiluteolytic conceptus interferon oTP-1. Ewes treated with recombinant bovine interferon-αI1 also had increased endometrial2′,5′-A synthetase activity, indicating that systemic administration of this interferon may directly affect the uterus and enhance fertility rate in ewes.