Prostacyclin formation by myometrial & decidual fractions of the pregnant rat uterus

Trapped Blood Elements Within the Decidua of the Rat Pregnant Uterus Generate a Lipoxygenase Product(s) Which Inhibits Myometrial Prostacyclin Synthesis

“…The present experiments clearly show that the separated decidual tissue fraction of the rat pregnant uterus synthesizes lesser amounts of prostacyclin than the myometrium in accordance with earlier studies (Williams et al, 1978;. This difference was originally attributed to differences in the concentrations of prostacyclin synthetase within these tissues (Williams et al, 1978).…”

“…If prostacyclin generation increases, then perfusion should be adopted routinely. The present results have also meant that the capability of the rat pregnant decidua to produce prostacyclin has had to be reassessed as the published data using non-perfused tissue are underestimates of the true synthetic capability (Williams et al, 1978).…”

“…This difference was originally attributed to differences in the concentrations of prostacyclin synthetase within these tissues (Williams et al, 1978). However, the finding that segments of whole uterus also produced much less prostacyclin than the myometrium alone suggested an inhibitory factor may be involved (synthesis was below that to be expected from the fact that approximately one third of the tissue weight is decidua producing less prostacyclin than the myometrium).…”

“…Decidual microsomes produced several arachidonic acid metabolites, the chief one being PGE2 whereas the major product of the myometrial preparations was 6-oxo-PGFIa (Downing & Williams, 1977) which is the hydrolysis product of the unstable prostacyclin (PGI2) (Johnson, Morton, Kinner, Gorman, McGuire, Sun, Whittaker, Bunting, Salmon, Moncada & Vane, 1976). Direct estimation showed that prostacyclin was produced in much larger quantities by the myometrium than the decidua (Williams, Dembinska-Kiec, Zmuda & Gryglewski, 1978) gested that prostaglandin cyclic endoperoxides produced by blood platelets may be utilised by the walls of blood vessels for conversion to prostacyclin. This finding raised the possibility that a similar mechanism may operate within the uterus where high cyclooxygenase activity within the decidua may produce cyclic endoperoxides which could be converted to prostacyclin within the myometrium, thereby 'boosting' its inherent synthetic capacity.…”

Inhibition by PGI-2 of myometrial activity in vivo in non-pregnant ovariectomized sheep

“…Several investigators have shown that PGI-2 is present in the myometrium of pregnant and non-pregnant animals and in women (Jones, Poyser & Wilson, 1977; Dembinska-kiec, Zmuda & Gryglewski, 1978;Omini, Folco, Pasargiklian, Fano & Berti, 1979). PGI-2 is also produced in the human placenta (Myatt & Elder, 1977) and in the fetal membranes (Satoh et al, 1981).…”