Abstract
Summary
Progesterone and its 3-cyclopentyl enol ether (PCPE) have been compared in a battery of biological tests. Orally or intraperitoneally administered PCPE was respectively 1/80th and 1/20th as active as subcutaneously injected progesterone in the Clauberg test. Oral doses of PCPE, 10–20 times those of subcutaneous progesterone were unable to maintain pregnancy in ovariectomized rats. Three to four times as much “pregnanediol” was detected in the urine of rabbits following oral administration of progesterone than a comparable dose of PCPE. Orally or intraperitoneally administered PCPE at doses 20–40 times those of effective doses of progesterone failed to potentiate the anesthetic effect of a subhypnotic dose of sodium hexobarbital. These data demonstrate that PCPE and progesterone have a markedly different biological profile and cast serious doubt on the possibility that biologically active amounts of PCPE are converted to and/or metabolized in the same way as progesterone, as claimed by others. Our data strongly support the view that if any transformation of PCPE to progesterone occurs, the likeliest site of this conversion is the gut.
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