The corpus luteum (CL) is a temporary endocrine gland, which goes trought different developmental phases: formation, maintenance and regression and reaches full secretory capacity when formation is complete. Steroidogenic profile differs over diestrus : progesterone (P4) is markedly elevated in the formation period; decreasing P4 and increasing 17b-estradiol (E2) are observed during maintenance and E2 highest diestrous levels on day 40 post ovulation (p.o.). Nevertheless, mechanisms regulating CL function and life span are not compeltely elucidated and show species specific differences. Special interest relies on the luteolytic phase, or regression phase, as some authors prefer when talking about the non-pregnant bitch, a moment that, differently from other species, PGF2a plays no important role. We hypothesize that E2 is one of the triggers for the non-pregnant dog luteolysis and that its variations over diestrus contribute to the establishement of metabolic alterations, specially insulin resistance. To test this hypothesis 24 non-pregnant bitches will be submitted to ovariosalpingohysterectomy on days 10, 20, 40, 60, 80 and 100 p.o. (n = 4 per group). Blood samples will be collected prior to anesthesia for hormonal measurements of P4, E2, insulin, prolactin, GH and LH and glycaemia will assessed as a metabolic parameter. Some CL will be frozen in liquid nitrogen for posterior gene and protein expression evaluation as microarray, real time PCR and western blotting. For immunhistochemistry CL samples will be fixed in 4% paraformaldehyde. Remaining CL will be transported to the laboratory in phospahte buffer for cell culture and E2 and/or E2 receptor blocker experiments. Genes involved in apoptosis, prolieferation and steroidogenesis, specially E2 and P4 receptors will be analyzed after cell treatments. Samples undergoing microarray analysis will be used to define other candidate genes related to luteal regression and metabolic alterations. At least 4 genes related to CL regression and 4 to metabolic alterations which have been differentially expressed will be validated through real time PCR, western blotting and immunhistochemistry. Data will be analyzed by MinitabÒ statistical program and differences will be considered when p < 0.05. (AU)
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MEDEIROS DE CARVALHO SOUSA, LIZA MARGARETH;
SILVA, RENATA DOS SANTOS;
DA FONSECA, VANESSA UEMURA;
LEANDRO, RAFAEL MAGDANELO;
DI VINCENZO, THIAGO SENNA;
ALVES-WAGNER, ANA BARBARA;
MACHADO, UBIRATAN FABRES;
PAPA, PAULA DE CARVALHO.
Is the canine corpus luteum an insulin-sensitive tissue?.
Journal of Endocrinology,
Web of Science Citations: 0.