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TRAPPED BLOOD ELEMENTS WITHIN THE DECIDUA OF THE RAT PREGNANT UTERUS GENERATE A LIPOXYGENASE PRODUCT(S) WHICH INHIBITS MYOMETRIAL PROSTACYCLIN SYNTHESIS
Author(s) -
TAHIR K.E.H. EL,
WILLIAMS K.I.
Publication year - 1981
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1981.tb16805.x
Subject(s) - decidua , prostacyclin , myometrium , endocrinology , medicine , uterus , arachidonic acid , chemistry , incubation , decidual cells , platelet , biology , biochemistry , enzyme , pregnancy , placenta , fetus , genetics
1 Prostacyclin (PGI 2 ) production by chopped segments of rat pregnant uterus was low compared with synthesis by separated myometrial tissue. Incubation of separated myometrium with decidua (2:1 by weight) led to an inhibition of myometrial PGI 2 output. 2 Boiling decidual tissue abolished the inhibitory influence on myometrial PGI 2 output. Preincubation of decidua with 5, 8, 11, 14‐eicosatetraynoic acid (ETA) (30 m̀g/ml) also suppressed decidual inhibitory activity but indomethacin (30 m̀g/ml) was ineffective. 3 Incubation of decidual and myometrial tissue with arachidonic acid (AA) 10m̀g/ml did not increase the inhibition of myometrial PGI 2 synthesis, even if the decidua were pre‐incubated with indomethacin. 4 Myometrial PGI 2 production was reduced if the chopped tissue was pre‐incubated with soya bean lipoxidase for 10 min at 4°C. This reduction was reversed if the lipoxidase was incubated with ETA (30°g/ml) for 30 min at 37°C before addition to the myometrial tissue. 5 Perfusion of the uterus to remove blood elements removed the inhibitory action that the decidua exerted upon myometrial PGI 2 production. PGI 2 synthesis by separated decidual and whole uterine tissue was markedly elevated. 6 The addition of rat blood platelets (0.75 × 10 9 /ml) to incubations of perfused decidual tissue reduced PGI 2 output and restored the inhibitory action that the decidua exerted on myometrial PGI 2 synthesis. 7 It is concluded that a lipoxygenase enzyme contained in blood platelets trapped within the decidual vasculature produces a hydroperoxy acid which inhibits decidual PGI 2 production or myometrial PGI 2 synthesis when the tissues are incubated together. It is suggested that perfusion is a pre‐requisite before study of PGI 2 synthesis in highly vascularised tissues. 8 The pathophysiological importance of such platelet lipoxygenase products is discussed.