Maintenance of Pregnancy in Spayed Rats with 20α-Hydroxypregn-4-ene-3-one and 20β-Hydroxypregn-4-ene-3-one

Pregnancy-Terminating Effect of Human Chorionic Gonadotrophin in Rats

“…Since the blood levels of progesterone, 20a-OHP or oestrogen were not measured in the present study, it is not known whether the levels of any of these steroids were affected following a single dose of HCG. In ovariectomized rats treated with HCG, daily doses of progesterone were able to protect normal implantations which indicated the efficacy of this steroid in maintaining pregnancy under that experimental condition (Talwalker et al, 1966). Progesterone failed to maintain pregnancy in HCG-treated intact rats; however, similar results were reported for PMSG-treated rats and hamsters by Yang & Chang (1968).…”

“…It is known that HCG stimulates ovarian production of oestro¬ gen (Gemzell, 1965;MacDonald, Armstrong & Greep, 1966), progesterone (Savard et al, 1965;Armstrong, 1968), and the enzymatic reduction of pro¬ gesterone to a metabolite, 20a-hydroxypregn-4-en-3-one (20a-OHP) (Wiest, Kidwell & Balogh, 1968). Although 20a-OHP possesses some progestational activity in biological assays (Zander, Forbes, Von Münstermann & Neher, 1958), it failed to support pregnancy in ovariectomized rats (Talwalker, Krähenbühl & Desaulles, 1966). Since the blood levels of progesterone, 20a-OHP or oestrogen were not measured in the present study, it is not known whether the levels of any of these steroids were affected following a single dose of HCG.…”

Progesterone Catabolism in the Rat Ovary: A Regulatory Mechanism for Progestational Potency During Pregnancy1

“…monal properties akin to those of progesterone (27)(28)(29), comparative bioassays have invariably shown the reduced steroid to be less potent (27)(28)(29)(30)(31)(32), and, as yet, its capacity to support pregnancy has not been demonstrated. Consideration of the weak or possibly nonexistent progestational activity of the reduced steroid and the correlation between 20a-OH-SDH activity and ovarian vein levels of 20a:-OH-P lead one to the conclusion that high enzyme activity may function physiologically to maintain a relatively low progestational potency of ovarian secretions during the estrous cycle.…”

Metabolic Clearance Rate and Production Rate of 20α-Hydroxypregn-4-en-3-one in the Menstrual Cycle

“…The biological activity of 20a-hydroxypregn-4-en-3-one (20a-OHP) has been shown to be one quarter to one half that of progesterone in the Clauberg and Hooker-Forbes tests [19], In rats and mice 20ce-OHP is incapable of supporting nidation [13,18]. It is also incapable o f maintaining or pro longing pregnancy in mice or rats [16,17] although relatively high doses will support embryo development and implantation in the rabbit [9].…”