ELUCIDATION OF REGULATION OF VASCULAR ENDOTHELIAL GROWTH FACTOR EXPRESSION IN THE LUTEAL DEVELOPMENT OF GOATS.

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In the first year of the research project (2001), changes of gene expression of the VFGF receptor, or Flk-1 and Flt-1 were examined during the development of caprine corpora lutea to elucidate any regulation mechanism of VEGF signaling system. The results showed that the gene expression of Flk-1, which seems to play a role for transduction of VEGF signaling, increased in the early stage of the luteal development. However, the gene expression of Flt-1, which seems to act as a decoy receptor for VEGF, did not change during the luteal development and increased in the period of luteal maintenance. These results suggest that VEGF may stimulate angiogenesis partly through a VEGF receptor, Flk-1, during The luteal development in the goat and that the signal transduction of VEGF may be regulated at the level of the receptor.In the second year of the research project (2002), to elucidate roles of prostaglandins (PG) in the development of caprine corpora lutea and to look for a method to regress … More the early corpora lutea, changes of gene expressions ofPG synthases and PGI_2 receptors, and effects of PG synthase inhibitors on luteal development were examined. As the results, it was shown that both mRNAs of the PGI_2 receptors, or IP-R and PPARδ increased in the early stage of the luteal development. Furthermore, the result also showed that the luteal development was partially inhibited by the direct administration of phenylbutazone, a PG inhibitor, into the corpus luteum just after ovulation, but the inhibition was not complete. These results suggest that PG, especially PGI_2, may play roles in the luteal development in the goat, but further studies are required to find a method for regression of the early corpus luteum.In conclusion, the present studies indicate a possibility that the increase of gene expression of a VEGF receptor, Flk-1, may participate in regulation of signal transduction of VEGF in the period of luteal development in goats. Besides, these studies suggest that PGs, especially PGI_2, may play a role in the luteal development. Less