Endocrine and molecular mechanisms by which estradiol stimulates endometrial prostaglandin F2α synthesis in the cow / Mecanismos endócrinos e moleculares pelos quais o estradiol estimula a síntese de prostaglandina F2α no endometrial em fêmeas bovinas

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

Estradiol (E2) is required for luteolysis in bovine female and E2 injections stimulate prostaglandin F2α (PGF2α) release. It is possible that E2 stimulates synthesis and/or activity of molecules in the cascade of PGF2α production, such as enzymes and receptors to other ligands. Calcium is a known cofactor for protein kinase C and phospholipase A2, enzymes involved in PGF2α production. The main goal of this study was to investigate endocrine and molecular mechanisms stimulated by E2 during luteolysis. In experiment 1, non-lactating Holstein cows were treated with 3mg E2 on days 13 (n=2), 15 (n=2), 17 (n=3) or 19 (n=5) of the day estrous cycle and production PGFM (a PGF2α plasma metabolite) was evaluated by radioimmunassay. It was concluded that E2 administration on day 17 of the cycle was an adequate experimental model to determine mechanisms involved in endometrial PGF2α synthesis. Experiment 2 was designed in order to investigate the role of E2 in the enzymatic cascade of PGF2α production. Cyclic, cross-bred beef heifers were paired on day 17 of a synchronized estrous cycle, injected with 0 (n=6) or 3mg of E2 (n=7) and slaughtered after two hours. Endometrial explants were treated with stimulators of the cascade of PGF2α synthesis, i.e., calcium ionophore (CI), melittin or oxytocin. Explants were incubated in quadruplicate and medium samples were collected immediately and 60min after to begin culture. The concentrations PGF2α were measured by radioimmunoassay. Endometrial explants in vitro treatment with CI production the PGF2α was 48,41% higher in from cows treated with E2 (P≤0,01). In experiment 3, bovine endometrium cells (BEND cells) were treated with 0, 10-7, 10-6 or 10-5M CI for 12h in triplicate, in three independent experiments. The 10-6 and 10-5M concentrations of CI stimulated production of PGF2α in comparison to other concentrations (P≤0,05). In experiment 4, BEND cells received 0 or 10-13M E2 and 0 or 10-6M CI in a 2 x 2 factorial arrangement, for 12h in triplicate cultures in three independent experiments. Production of PGF2α was 33.1, 32.5, 92.4 and 145.6 (pooled SEM: 21.8) pg/mL for cells treated with nothing, E2, CI and E2 + CI, respectively. Treatment with CI alone tended to stimulate PGF2α production (P≤0,08), however, in the presence of E2, CI significantly stimulated PGF2α synthesis (P≤0,01). It was concluded that in bovine female the E2 improved the CI effects in endometrial PGF2α synthesis. It proposes that E2 active the enzyme synthesis that, calcium stimulated, actuate in endometrial PGF2α synthesis

ASSUNTO(S)

pgf2&alpha estradiol bovinos estradiol endométrio luteólise luteolysis pgf2&alpha bovine endometrium

ACESSO AO ARTIGO

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