Gene Expression in Endocrine Tissues
(M505) GLUT 1 AND GLUT 4 mRNA AND PROTEIN IN THE DOG CORPUS LUTEUM DURING DIESTRUS.
Paarmann, Fabio A1, Marques Jr, Jose E B1, Barros, Rodrigo P A1, Machado, Ubiratan F1, Campos, Danila B1, Papa, Paula C1, 1 University of Sao Paulo, Sao Paulo, Brazil
ABSTRACT- Bitch estrous cycle has specific peculiarities as functional corpus luteum (CL) lasts approximately sixty days. Maintenance of high metabolic rates is due, in most of tissues, to increased glucose transport and utilization. Glucose transporters (GLUTs) belong to a family of proteins showing a tissue-specific distribution. In the ovaries, GLUT 1 and GLUT 4 were localized in growing follicles while CL expressed only the GLUT 1 isoform. The aim of this study was to identify possible candidates for the transport of glucose in the CL of the dog during diestrus. For that purpose 28 healthy mongrel bitches were submitted to ovariosalpingohysterectomy (OSH) on days 10, 20, 30, 40, 50, 60 and 70 after ovulation, which was determined through plasma progesterone concentrations assessment. Ovaries were collected and dissected, corpora lutea were perfused with NaCl 0.9% using sterile needle and frozen in liquid nitrogen for subsequent mRNA and protein extraction. GLUT 1 and GLUT 4 protein content in dog CL were measured using Western blot while mRNA was assessed using Northern blotting. Rectus abdominis muscle was used as positive control for both transporters. Blood samples were collected before animals were anesthetized for analysis of progesterone (P4), estradiol-17 (E2), insulin and glucose. GLUT 4 protein and mRNA could not be detected in any studied time point while GLUT 1 protein and mRNA were present during all diestrus, although different phases showed no significant expression variations. P4 and E2 concentrations showed cycle specific variations all over the studied phase. Plasma glucose and insulin concentrations were elevated at 40 days after ovulation. Present data indicate that glucose transport in luteal cells from the diestrus phase is not related to GLUT 4, an insulin sensitive glucose transporter. Absence of cycle specific GLUT 1 variations, regardless of CL synthesis activity, is not in agreement with observations of E2 GLUT 1 dependent expression. Nevertheless, the same pattern of GLUT1 and GLUT 4 expression was described for the bovine CL, indicating that this transporter may be involved in basal glucose transport to corpus luteum.
KEY WORDS: corpus luteum, dog, glut 1, glut 4