Formation of (3H)-PGF2 alpha and (3H)-13, 14,dihydro-15-keto-PGF2 alpha from (3H)-PGE2 by the supernatant of uterine homogenates from estrous and ovariectomized rats, was studied, using the reaction system PGE2 + NADPH + (3H)-PGE2 + supernatant. Enzymatic conversion was lower in uterine supernatants from spayed rats than in uterine homogenates of rats at natural estrus. Spayed animals were injected with progesterone (P) or with estradiol-17-beta (Eo) at a dose of 1.0 or 50.0 micrograms. Conversion of (3H)-PGF2 alpha to (3H)-PGE2 or to (3H)-13, 14,dihydro-15-keto-PGF2 alpha did not differ in control ovariectomized or ovariectomized rats receiving P or 1.0 micrograms Eo. However, 50.0 micrograms Eo induced a significant conversion after 30 (P less than 0.01) and 60 (P less than 0.001) min of incubation. It is concluded that Eo, at the 50.0 micrograms dose, but not the 1.0 microgram dose of Eo, nor progesterone, stimulated conversion of (3H)-PGE2 into (3H)-PGF2 alpha or (3H)-13, 14,dihydro-15-keto-PGF2 alpha, presumably through the activity of the enzyme PGE2-9-keto-reductase.
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