This study was conducted to estimate the effects of kisspeptin-10 on blood concentrations of LH and GH in prepubertal dairy heifers. Heifers received a single injection of 1 mg kisspeptin-10 (nZ5) or saline (nZ5) intravenously, and serial blood samples were collected at 15-min intervals to analyze the response curves of both LH and GH after injection. Peakshaped responses were observed for concentrations of LH and GH, and the peaks were observed at 27G3 and 75G9 min, respectively, after injection, only in heifers injected with kisspeptin-10.
The aim of the present study was to determine the possible roles of chemokines in regulating bovine endometrial function during early pregnancy. The expression of six chemokines, including CCL2, CCL8, CCL11, CCL14, CCL16, and CXCL10, was higher in the endometrium at 15 and 18 days of pregnancy than at the same days in non-pregnant animals. Immunohistochemical staining showed that chemokine receptors (CCR1, CCR2, CCR3, and CXCR3) were expressed in the epithelial cells and glandular epithelial cells of the bovine endometrium as well as in the fetal trophoblast obtained from a cow on day 18 of pregnancy. The addition of interferon-τ (IFNT) to an endometrial tissue culture system increased CCL8 and CXCL10 expression in the tissues, but did not affect CCL2, CCL11, and CCL16 expression. CCL14 expression by these tissues was inhibited by IFNT. CCL16, but not other chemokines, clearly stimulated interferon-stimulated gene 15 (ISG15) and myxovirus-resistance gene 1 (MX1) expression in these tissues. Cyclooxygenase 2 (COX2) expression decreased after stimulation with CCL8 and CCL14, and oxytocin receptor (OTR) expression was decreased by CCL2, CCL8, CCL14, and CXCL10. Collectively, the expression of chemokine genes is increased in the endometrium during early pregnancy. These genes may contribute to the regulation of endometrial function by inhibiting COX2 and OTR expression, subsequently decreasing prostaglandin production and preventing luteolysis in cows.
Angiogenesis is involved in the local mechanisms that regulate follicular development and ovulation. Recently, the angiopoietin (ANPT)-Tie system has been shown to be required to regulate angiogenesis and blood vessel regression. Expression of the ANPT-Tie system in the cyclic ovary suggests that the relative changes in the expression of ANPT-1 and ANPT-2 influence the stability of ovarian blood vessels. In this study, we investigated 1) the mRNA expression for ANPT-1, ANPT-2, and endothelial cell-specific receptors Tie1 and Tie2 in the theca interna (TI) of the bovine developing, mature, and atretic follicles by using a semiquantitative reverse transcription polymerase chain reaction assay and 2) the effect of ANPT on the secretion of steroid hormones from bovine preovulatory follicles in vitro using a microdialysis system (MDS) implanted in the thecal layer. Bovine follicles were classified as developing, mature, and atretic according to size, follicular fluid content of estradiol (E2) and progesterone (P4), and characteristics of granulosa cells (GCs). Both ANPT and Tie mRNA were expressed in the TI, whereas GCs expressed ANPT mRNA only. The expression of ANPT-2 mRNA was decreased in the mature follicles. This decrease resulted in a decrease in the ANPT-2:ANPT-1 ratio (an index of instability of blood vessels), indicating that the blood vessels became more stable or mature. The early atretic follicles showed a higher ANPT-2:ANPT-1 ratio and higher Tie2 mRNA expression than did other follicles at healthy or later atretic stages. This finding may imply that blood vessels become unstable at the initial stage of follicular atresia. In both mid and late atretic follicles, Tie2 mRNA expression dramatically decreased, indicating a disruption of the ANPT-Tie system. In the MDS experiment, an infusion of ANPT-1 or ANPT-2 increased P4 release, whereas both ANPTs inhibited the release of androstenedione. ANPT-1 also increased E2 release. These results showed that the mRNA expression for ANPT-1, ANPT-2, Tie1, and Tie2 changes during follicular development, maturation, and atresia in bovine follicles and that ANPTs affect steroidogenesis in the preovulatory follicle. The results suggest that the ANPT-Tie system is involved the structural (angiogenesis) and secretory changes that occur during follicular development and atresia.
Abstract. Increase in the blood supply to individual follicles appears to be associated with follicular growth rates and the ability to become the dominant follicle, while reduced thecal vascularity appears to be closely associated with follicular atresia. Therefore, this study aimed to determine the real-time changes in the vascularity of the follicle wall during the first follicular wave in cycling Holstein cows. Normally cycling and lactating cows (n=5) were examined by transrectal color Doppler ultrasonography (the sensitivity for velocity: > 2 mm/sec) to determine the changes in the vasculature of the follicle wall (presence or absence of blood flow) and the diameter of follicles. A new follicular wave and ovulation were induced by GnRH injection at 48 h after an injection of PGF2α analogue. The ovaries were scanned daily for 7 days after GnRH injection. Follicles >2.5 mm were classified into 3 groups by the changes in diameter as follows: 1) largest follicle, 2) second largest follicle, and 3) small follicles, which included all other follicles >2.5 mm. Before the follicle selection, there was no significant difference in the percentage of follicles with detectable blood flow between the subsequently determined largest and second largest follicles. After the follicle selection, the percentage of follicles with detectable blood flow significantly decreased among the second largest follicles. In addition, small follicles with detectable blood flow kept larger diameters than those without detectable blood flow from one day before the occurrence of follicle selection. It is likely that maintenance of follicle vasculature and appropriate blood supply to the larger follicles is essential for follicle dominance. In small follicles, the presence of blood flow within the wall also appears to be required for recruitment. Consequently, the data suggest that the change of the blood supply to an individual follicle closely relates to the dynamics of follicular growth in the first follicular wave in the cow.
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