Prostaglandins And Uterine Bleeding

 

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There is little information about haemostatic function in the uterus in relation to menstrual bleeding. We measured platelet count and platelet retention in glass-bead columns, and plasma levels of FPA, TxB₂ and 6-oxo-PGF_1α in samples taken simultaneously from uterine vein (UV) and peripheral vein (PV) in 18 women (2 post-menopausal) undergoing hysterectomy. Platelet counts and FPA concentrations were similar in both sets of samples. Plasma levels of 6-oxo- PGF_1α were significantly (p<0.01) higher in UV (1.34 ± 1.27 ng/ml, mean ± SD) than in PV (0.18 ± 0.39 ng/ml) as were levels of TxB₂ (0.46 ± 0.54 and 0.1 ± 0.13 ng/ml). Platelet retention in UV blood was about half that observed in PV blood and the degree of platelet retention correlated inversely with plasma concentration of 6-oxo-PGF_1α (r = -0.48, p<0.01). There was a highly significant (p<0.01) rank order between the time since menstruation and plasma 6-oxo-PGF_1α concentration in UV blood. TxB₂ levels were highest on day 4 and then fell suddenly with time since menstruation. The results indicate that prostaglandins may modulate uterine bleeding at menstruation. Release of PGI₂ from uterine vessels could contribute to the lack of platelet deposition in the menstruating uterus and by this mechanism to the persistence of menstrual bleeding.