Comparison of protective effects of ethylestrenol, norbolethone, and spironolactone against lethality from acute doses of parathion and paraoxon in female rats.

Protection against the toxicity of parathion (increased LD50) was provided by preadministered ethylestrenol and, to a lesser extent, by norbolethone and spironlactone. Ethylestrenol and norbolethone also offered protection against paraoxon toxicity. With ethylestrenol and spironolactone, the protection against parathion lethality was greater than that against paraoxon lethality.