The canine corpus luteum (CL) functions as a source of progesterone (P 4 ) and 17b-oestradiol (E 2 ); however, the transport of energy substrates to maintain its high hormonal output has not yet been characterised. This study involved the localisation and temporal distribution of the facilitative glucose transporter 1 and the quantification of the corresponding protein (GLUT1) and gene (SLC2A1) expression. Some GLUT1/SLC2A1 regulatory proteins, such as hypoxia-inducible factor 1a (HIF1A) and fibroblast growth factor 2 (FGF2); mRNAs, such as HIF1A, FGF2 and vascular endothelial growth factor A (VEGFA); and VEGFA receptors 1 and 2 (FLT1 and KDR) were also analysed from days 10 to 70 after ovulation. Additionally, plasma P 4 and E 2 levels were assessed via chemiluminescence. Moreover, the canine KDR sequence has been cloned, thereby enabling subsequent semi-quantitative PCR analysis. Our results demonstrate time-dependent variations in the expression profile of SLC2A1 during dioestrus, which were accompanied by highly correlated changes (0.84!r!0.98; P!0.03) in the gene expression of HIF1A, VEGF and FLT1 as well as in P 4 plasma concentrations. FGF2 mRNA correlated with E 2 plasma concentrations (rZ0.61; PZ0.01). Our data reveal that the glucose transporter is regulated throughout the CL lifespan and suggest that CL depends on the sensing of hypoxia and the status of luteal vascularisation. Moreover, time-dependent expression of GLUT1/SLC2A1 may lie underneath increased metabolic and energetic requirements for sustaining P 4 production.

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HOMA apresentou-se mais alto aos 40 dias, associado aos menores valores de expressão do GLUT4. Por outro lado, obtivemos o pico de expressão de GLUT4 aos 50 dias, quando o índice HOMA apresentou valores baixos. Sugere-se que a queda da P4 associada à elevação do estradiol plasmático possa influenciar o índice HOMA. Pode-se concluir que a expressão do GLUT4 no corpo lúteo de cadelas segue o padrão observado para tecidos sensíveis à insulina, nos quais existe uma maior expressão durante a fase de maior sensibilidade à insulina e diminuição drástica em fase de pré ou já instalada resistência insulínica.Palavras-chave: Cadelas. Diestro. GLUT4. PCR tempo real. The canine estral cycle differs from other domestic species. Some studies demonstrated that the increase of the plasmatic concentration of progesterone during canine luteinic phase can lead to metabolic alterations, such as insulinic resistance and may cause complications such as Diabetes mellitus. Glucose is a molecule that is transported in most cells by transporting proteins. The process of installation of the insulinic resistance is characterized by tissue alterations of the expression of some glucose transporting proteins, as GLUT4. Currenly, 13 isoforms of transporting proteins were sequenced (GLUT1 to GLUT13). GLUT4 is present mainly in muscle and fat tissue. In order to assess if GLUT4 expression is present in luteal cells, and if this expression is related to P4 and E2 production, 28 bitches were divided into 7 groups, in accordance with the days after the ovulation -p.o. (from 10 to 70 days, n=4 for group). The ovaries were dissected and frozen in liquid nitrogen. The RNA was extracted and the cDNA was made and submitted to real time PCR. GAPDH gene was used as endogenous conntrol to standardization of target gene expression. Blood was collected to glycemia, insulinemia, P4, and E2β dosage. To assess the positive regulation of GLUT4, we also assessed HIF-1α mRNA