The effect of progestin- containing extracts of corpora lutea on uterine motility in the unanesthe-tized rabbit, with observations on pseudopregnancy
Reynolds, S.R.M.; Allen, W.M.
Arner Jour Physiol 102(1): 39-55
Subcutaneous injection of progestin (1/5 rabbit unit) into non-castrated rabbits whose uteri show marked motility causes marked diminution of motility in 2-24 hrs. When injected for 2 or 3 days, complete quiescence supervenes. Motility returns 2-5 days after withdrawal of progestin. In castrated adults, 4.8-5.0 rabbit units of progestin inhibit uterine motility in response to the intravenous injection of 1000 r.u. theelin per kgm.; 1.6 rabbit units of progestin prevent motility following 100-200 r.u. of theelin per kgm., but not to 500 r.u. Progestin extracts inactivated by alkali do not prevent motility following theelin (5 r.u. per kgm.). Theelin (200 r.u. per diem) for the first 5 days of pseudopregnancy inhibits endo-metrial proliferation despite the formation of corpora lutea that are histologically normal and which inhibit theelin-motility. The hormone responsible for this inhibition is chemically similar to if not identical with progestin, for alcoholic KOH destroys both properties of the corpus luteum extracts as regards endometrial proliferation and uterine motility.