Expression and localization of mRNA for the VEGF system and FP receptor in porcine corpora lutea.
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Date
2002-04-30
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Abstract
The purpose of this research was to establish a complete cDNA sequence for porcine prostaglandin F2a receptor (FPr), and to examine the expression and localization of FPr and components of the VEGF system in the porcine CL throughout the estrous cycle.
FPr cDNA was isolated and cloned from porcine CL. This isolate (Genbank accession number U91520) contains an open reading frame of 1086 bases coding for a protein of 362 amino acids with seven potential transmembrane domains. The predicted amino acid sequence of the porcine FPr had 83% homology with the FPr amino acid sequence for sheep, cattle and humans. The phylogenetic tree of prostanoid receptor family members clustered porcine FPr into the same group with other mammalian FPr, with the closest relationship to ovine and bovine FPr.
Northern blot analysis revealed a single transcript of ˜5 kilobases for FPr message. The signals of FPr mRNA expression were observed throughout the estrous cycle. Relatively weak signals of FPr mRNA expression were detected on day 4 and day 7 of the estrous cycle. The signal was greater (p<0.05) on day 10, day 13 and day 15 than day 4 or day 7. In situ hybridization analysis revealed that mRNA for ovarian FPr was expressed predominantly in the CL. Cellular localization of the FPr signals was primarily in steroidogenic large luteal cells. The FPr signals were also present in small cells, morphologically similar to (steroidogenic) cells which expressed LH receptor message.
Expression mRNAs for vascular endothelial growth factor (VEGF), VEGF receptor 1 (VEGFR-1) and VEGF receptor 2 (VEGFR-2) were observed in porcine CL throughout the estrous cycle. Northern blot analysis revealed single transcripts of approximately 3.9-kb, 7-kb and 5-kb for VEGF, VEGFR-1 and VEGFR-2 respectively. Signals for VEGF mRNA expression were consistent throughout the cycle. Relatively weak signals of VEGFR-1 mRNA expression were observed on day 4. Signal intensity increased on day 7, and obtained higher levels (P<0.05) on days 10, 13 and 15. In contrast, relative levels of VEGFR-2 mRNA were lower on day 4 than on day 7, peaked on day 10, remained unchanged on day 13, and decreased (P<0.05) on day 15. In situ hybridization revealed that VEGF mRNA was localized predominantly in large luteal cells, whereas VEGFR-1 and VEGFR-2 were limited to small endothelial-like cells.
Collectively, the results provide information on: 1) a complete cDNA sequence for porcine FP receptor; 2) the expression and localization of mRNA for luteal FPr, which indicated that the number of luteal FPr contributes to the acquisition of luteolytic capacity in the pig; 3) the expression and localization of mRNA for VEGF, VEGFR-1 and VEGFR-2, which suggested that the VEGF system plays a role in angiogenesis and maintenance of vasculature in porcine CL.
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FP receptor, pigs, VEGF, PGF<sub>2<font face="symbol">a</font></sub>, corpus luteum
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Degree
PhD
Discipline
Physiology
