PRODUCTION OF PROSTAGLANDINS BY THE PSEUDOPREGNANT RAT UTERUS, in vitro, AND THE EFFECT OF TAMOXIFEN WITH THE IDENTIFICATION OF 6‐KETO‐PROSTAGLANDIN F1α AS A MAJOR PRODUCT

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Abstract
Prostaglandin production by rat uterus homogenates has been studied, in vitro, on days 2 to 13 of pseudopregnancy. The highest production of prostaglandins occurred on day 5. The amounts of prostaglandins F and D formed were higher than the amounts of prostaglandin E on every day studied. The ratios of prostaglandins F and D to prostaglandin E produced steadily decreased up to day 6. It then increased with the highest values occurring between days 10 and 13. Progesterone levels in peripheral plasma increased rapidly from days 2 to 5, remained high up to day 9, then steadily decreased between days 10 and 13. The anti‐oestrogenic drug, tamoxifen administered on day 2, significantly inhibited the increase of prostaglandin production which occurred on day 5. Prostaglandin E production was inhibited more than the production of prostaglandins F and D. Analysis of the uterine extracts by gas chromatography and mass spectrometry showed prostaglandin F2α, F1α (in trace amounts), E2 and D2 to be present. The major product detected was 6‐keto‐prostaglandin F1α. Its identification forms an addendum to the paper. Also present as a major product was 6(9)‐oxy‐11,15‐dihydroxyprosta‐7,13‐dienoic acid.