Insulin-like growth factors in sheep uterine fluids: concentrations and relationship to ovine trophoblast protein-1 production during early pregnancy

Ko, Y.; Lee, C.Y.; Ott, T.L.; Davis, M.A.; Simmen, R.C.M.; Bazer, F.W.; Simmen, F.A.

Insulin-like growth factors in sheep uterine fluids: concentrations and relationship to ovine trophoblast protein-1 production during early pregnancy

1991

Uterine luminal fluids (ULFs) from Days 10, 12, 14, and 16 cyclic (C) and pregnant (PX) ewes were analyzed for presence of insulin-like growth factors (IGF-I, IGF-II) and other mitogenic factor(s). IGF content and non-IGF mitogenic activity were measured by IGF RIAs after removal of IGF binding proteins and by stimulatory effects on DNA synthesis of density arrested AKR-2B cells, respectively. ULF IGF-I content was not different between days, but differences in IGF-I between C and PX groups at Day 16 (C > PX) were found (p < 0.05). ULF IGF-II content was not different between C and PX ewes; however, differences among days (p < 0.01) were apparent. In both C and PX ewes, Day 14 ULF had highest IGF-II content (C: 4.60 +/- 0.98 ng/ml, PX: 5.39 +/- 1.38 ng/ml). in Day 12 and Day 14 (C and PX) ULF, IGF-II concentration was about 10-fold greater than that of IGF-I. 1. AKR-2B mitogenic activity, in ULF differed among days (p < 0.01), but not between C and PX ewes. Highest activity was observed for Day 14 C and PX ULF, whereas lowest activity was for Day. 10 C and Day 16 PX ULF. Sephadex G-200 gel-filtration chromatography of ULF from Day 14 PX ewes demonstrated mitogenic activity in the column void volume fractions and in the 30-kDa size range of eluted proteins. Day 13 conceptuses were cultured in serum-free medium to define the effect of exogenous IGFs on ovine trophoblast protein-1 (oTP-1) secretion. Amount of oTP-1 in conceptus culture medium was measured by RIA. Neither IGF-I nor IGF-II alone had any effect on oTP-1 secretion; however, simultaneous addition of both factors significantly increased oTP-1 secretion (p < 0.01). Results demonstrate the presence of IGF-I and IGF-II as well as other high Mr fibroblast mitogens in ovine ULF, and the stimulatory effect of combined IGFS on oTP-1 secretion in vitro. This suggests the potential involvement of peptide growth factors in peri-attachment conceptus development in sheep.

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