Mechanisms Regulating Prostaglandin F2 Secretion from the Bovine Endometrium

Abstract

The mechanism that regulates luteolytic PGF2 alpha secretion as stimulated by oxytocin is thought to involve induction of the inositol (1,4,5)-trisphosphate-diacylglycerol second messenger system, which mobilizes intracellular calcium and activates protein kinase C. In Experiment 1, endometrial explants taken from heifers on d 18.5 to 19.5 postestrus had increased PGF2 alpha secretion after treatment with 1 microM calcium ionophore A23187 to increase intracellular calcium, 100 nM phorbol 12-myristate 13-acetate to activate protein kinase C, and 100 nM oxytocin. The stimulatory effects of oxytocin and calcium ionophore A23187 plus phorbol 12-myristate 13-acetate did not differ from each other. In Experiment 2, endometrial explants taken from cows on d 18.5 to 19.5 postestrus had increased PGF2 alpha secretion after treatment with 0.2 and 2 microM thapsigargin to mobilize intracellular calcium that was sensitive to inositol (1,4,5)-trisphosphate. Secretion of PGF2 alpha was also increased by 100 nM oxytocin and was influenced by the interaction of thapsigargin and oxytocin such that 100 nM oxytocin did not further increase the secretion of PGF2 alpha in the presence of 2 microM thapsigargin. In Experiment 3, 100 nM oxytocin stimulated greater production of inositol trisphosphate and total inositol phosphates in the endometrium of cyclic cows than in the endometrium of pregnant cows on d 16.5 to 17.0 postestrus, although luteolysis was not yet initiated in the cyclic cows. These results are consistent with the hypothesis that the activation of the inositol (1,4,5)-trisphosphate-diacylglycerol second messenger system by oxytocin is involved in the stimulation of PGF2 alpha secretion from the endometrium during late diestrus in cows.

Local and Systemic Effects of Embryos on Uterine Tissues During Early Pregnancy in Pigs

“…The uterine response to OT depends on expression of OTR mRNA and protein [7,[17][18][19] and on generation of the second messengers inositol triposhate and diacyloglycerol [7,18,20,21]. OT also stimulates PGF2α secretion from the bovine endometrium through a previously discussed signaling pathway [22][23][24][25].…”

“…The uterine response to OT depends on expression of OTR mRNA and protein [7,[17][18][19] and on generation of the second messengers inositol triposhate and diacyloglycerol [7,18,20,21]. OT also stimulates PGF2α secretion from the bovine endometrium through a previously discussed signaling pathway [22][23][24][25].It has previously been shown that OT acts on the porcine endometrium as a regulator of secretion of both luteolytic PGF2α [3,6] and luteotrophic PGE2 [6]. Progesterone (P4) inhibits OTstimulated production of endometrial and myometrial PG via mechanisms including regulation of OTR expression, inositol phosphate accumulation and intracellular Ca 2+ response [7,19,26,27].…”

<b>Ação do 17&#946;-estradiol na síntese de PGF2&#945; endometrial em vacas</b>

“…A ligação da ocitocina (OT) ao seu receptor aciona uma complexa via de síntese de PGF2α (MCCRACKEN; CUSTER; LAMSA, 1999). Os OXTRs são receptores acoplados à proteína Gqα, sua ativação estimula a fosfolipase C (PLC) que atua na membrana celular hidrolisando fosfatidil-inositol bisfosfato em Inositol 1,4,5 trifosfato (IP3) e 1,2 diacilglicerol (DAG) (TYSSELING et al, 1997 quinases reguladas por sinal extracelular (ERK1/2) e fosfolipase A2 (PLA2).…”

Effect of dietary polyunsaturated fatty acids on uterine prostaglandin synthesis in the cow

“…The calcium ionophore A23187 (CaI) promotes calcium flux across membranes and activates PLA 2 . It can also stimulate PG synthesis in the bovine endometrium (Danet-Desnoyers et al 1995, Tysseling et al 1998.…”