Anti-progestational action of norethindrone-oxime in rabbits
Abstract
Relative binding affinities (RBA) of norethindrone-oxime (NETO) and norethindrone (NET) measured by dextrancoated charcoal adsorption were in the following order: NET>progesterone>NETO. Both NETO and NET exhibited a competitive inhibition with the binding of progesterone on its receptor-like sites. In addition, NETO possessed a significant anti-progestational action, while NET did not show an effect even at a dose as high as 16 mg. These results indicated that NETO antagonized progesterone at receptor level and it was assumed that oximation of NET at C3 increased its antiprogestational activity.
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