To determine whether glucocorticoids (GCs) play a role in regulating uterine function in cow, the present study examined the expression of mRNA encoding GC receptor (GC-R) a, 11b-hydroxysteroid dehydrogenase (11-HSD) type 1 and type 2, and the activity of 11-HSD1 in bovine endometrial tissue throughout the estrous cycle. We also studied the effects of cortisol on basal, oxytocin (OT)-and tumor necrosis factor-a (TNFa)-stimulated prostaglandin (PG) production. A quantitative real-time PCR analysis revealed that GC-Ra mRNA was expressed more strongly in the mid-luteal stage (days 8-12) than in the other stages. In contrast to GC-Ra mRNA expression, 11-HSD1 mRNA expression was greater in the follicular stage than in the other stages, whereas 11-HSD2 mRNA expression was lowest in the follicular stage. The activity of 11-HSD1 was greater in the follicular stage and estrus than in the other stages and was lowest in the mid-luteal stage. Cortisone was dosedependently converted to cortisol in the cultured endometrial tissue. Although cortisol did not affect either the basal or OT-stimulated production of PGs in the cultured epithelial cells, the production of PGs stimulated by TNFa in the stromal cells was suppressed by cortisol (P!0 . 05). Cortisol suppressed basal prostaglandin (PG)F2a without affecting basal PGE2 production in the stromal cells. The overall results suggest that the level of cortisol is locally regulated in bovine endometrium throughout the estrous cycle by 11-HSD1, and that cortisol could act as a luteoprotective factor by selectively suppressing luteolytic PGF2a production in bovine endometrium.

Low oxygen caused by a decreasing blood supply is known to induce various responses of cells, including apoptosis. The present study was conducted to examine whether low-oxygen conditions (hypoxia) induce luteal cell apoptosis in cattle. Bovine midluteal cells incubated under hypoxia (3% O(2)) showed significantly more cell death than did those incubated under normoxia (20% O(2)) at 24 and 48 h of culture, and had significantly lower progesterone (P4) levels starting at 8 h. Characteristic features of apoptosis, such as shrunken nuclei and DNA fragmentation, were observed in cells cultured under hypoxia for 48 h. Hypoxia increased the mRNA expressions of BNIP3 and caspase 3 at 24 and 48 h of culture. Hypoxia had no significant effect on the expressions of BCL2 and BAX mRNA. Hypoxia also increased BNIP3 protein, and activated caspase-3. Treatment of P4 attenuated cell death, caspase-3 mRNA expression, and caspase-3 activity under hypoxia. Overall results of the present study indicate that hypoxia induces luteal cell apoptosis by enhancing the expression of proapoptotic protein, BNIP3, and by activating caspase-3, and that the induction of apoptosis by hypoxia is partially caused by a decrease in P4 production. Because hypoxia suppresses P4 synthesis in bovine luteal cells, we suggest that oxygen deficiency caused by a decreasing blood supply in bovine corpus luteum is one of the major factors contributing to both functional and structural luteolysis.

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Abstract. Vascular endothelial growth factor (VEGF) is a well known angiogenic factor that has been suggested to play some physiological roles in reproductive organs. To clarify whether VEGF is involved in regulating bovine endometrial function locally, in experiment 1, we determined the expression of VEGF, VEGF receptor (VEGFR) 1 and VEGFR2 throughout the estrous cycle in endometrial tissues. Endometrial tissue was collected at estrus (Day 0), the early I (Days 2-3), early II (Days 5-6), mid and late luteal stages and the follicular stage . RT-PCR and Western blotting analysis revealed that VEGF mRNA expression at estrus was higher than at the early I, early II and late luteal stages (P<0.05), whereas VEGF protein content was greatest at the early I luteal stage and decreased thereafter. VEGFR1 mRNA expression was lower at estrus and at the early I and early II luteal stages than at the other stages, whereas VEGFR1 protein expression did not change significantly throughout the estrous cycle (P<0.05). VEGFR2 mRNA expression was higher at the mid and late luteal stages than at the early I and early II luteal stages, and VEGFR2 protein was higher at the mid and late luteal stages than at estrus (P<0.05). In experiment 2, to determine the effect of VEGF on prostaglandin (PG) F2α and PGE2 production by endometrial cells, cultured endometrial epithelial and stromal cells were exposed to VEGF (0, 5, 50, 100 and 200 ng/ml) for 24 h. VEGF (200 ng/ml) stimulated PGF2α production by stromal cells (P<0.05), but not PGE2 production. VEGF did not affect PG production by endometrial epithelial cells. The overall results suggest that VEGF and its receptors are regulated throughout the estrous cycle and that VEGF participates in the local regulation of bovine endometrial function by a selective modulation of PGF2α production in stromal cells in an auto-and/or paracrine manner. Key words: Bovine, Endometrium, Estrous cycle, VEGF, VEGF receptors (J. Reprod. Dev. 56: [223][224][225][226][227][228][229] 2010) ascular endothelial growth factor (VEGF) is a well known angiogenic factor that plays important physiological roles in a wide range of cells and tissues [1]. In reproductive organs, VEGF is required for normal ovarian angiogenesis and growth of the endometrium throughout the ovulatory cycle in humans [2,3] and rodents [4,5]. In addition, the vascular hyperpermeability induced by VEGF seems to be essential for normal implantation in rodents [6]. The above findings suggest that VEGF has pivotal roles in regulating the functions of the cyclic and pregnant endometrium. In cows, VEGF expression has been observed in the ovary [7,8] The biological actions of VEGF are mediated by two types of tyrosine kinase receptors, VEGFR1 (Flt-1) and VEGFR2 (Flk-1/ KDR) [1,11]. VEGFR1 has a high affinity for VEGF, and its signal for angiogenesis is weak [12]. Although VEGFR1 mediates an essential signal for normal vascularization, it seems that VEGFR1 does not mediate stimulation of endothelial cell proliferation [13]. The exact function of ...