Antioestrogenic action of the aldosterone antagonist canrenoate K in the rat (adenohypophysis, ceruloplasmin).

In a dose of 7,k mg/rat/day in food, the aldosterone antagonist canrenoate K inhibited the adenohypophyseal reaction (growth, raised thyroxine-binding capacity of the adenohypophyseal proteins in vitro) and the ceruloplasmin reaction (elevation of the serum ceruloplasmin level) to three weeks' intramuscular administration of long-acting oestradiol benzoate in doses of 1 mg twice a week. The effect was similar to that of the antioestrogen clomiphen in a dose of 1.25 mg/rat/day in food. In combined administration of clomiphen and canrenoate K, no summation of their effect was observed. Neither canrenoate nor clomiphen affected the post-oestradiol drop in body weight, but they both potentiated the oestradiol-induced decrease in testicular weight and canrenoate potentiated the effect of oestradiol on uterine weight. It was therefore concluded that the effect of canrenoate is not of a catatoxic nature, i.e. that it is not determined by increased metabolic degradation of oestradiol.