The concentrations of prostaglandins in endometrium during the menstrual cycle in women with measured menstrual blood loss.

The concentrations of PGF2 alpha, PGE2 and 6-oxo-PGF1 alpha were measured in human uterine tissues during the menstrual cycle. The concentrations of all PGs in endometrium were greater than in myometrium. PGF2 alpha, which was found in the greatest concentrations, was high in the mid-secretory phase in both endometrium and myometrium. The concentration of PGE2 did not vary during the menstrual cycle in either tissue. The biosynthetic capacity of endometrium to produce both PGF2 alpha and PGE2 was significantly greater in the mid than the late secretory phase in the presence of exogenous arachidonic acid. Also, in spite of low endogenous concentrations, both endometrium and myometrium were able to produce significant amounts of 6-oxo-PGF1 alpha during a 30 minute incubation. The possible significance of this late secretory decline in the capacity of the endometrium to produce PGF2 alpha and PGE2 is discussed.