Modulation of the effect of oestradiol on adenohypophyseal weight: ineffectiveness of nickel chloride, potentiation by cimetidine.

Male rats received an i.m. injection of oestradiol benzonate twice a weak, as an aqueous microcrystal suspension in doses of 1 mg, and/or were given, in their food, nickel chloride in daily doses of 10 mg [first experiment] or 20 mg [second experiment] per rat, or cimetidine, an antagonist of H2 receptors, in daily doses of 20 mg [first experiment] or 40 mg [second experiment] per rat. Neither dose of nickel chloride affected the oestrogen-induced growth reaction of the adenohypophysis, the increase in polyphenol oxidase [ceruloplasmin] activity in the blood [the larger dose stimulated it slightly], the increase in hypothalamic polyphenol oxidase activity or the post-oestrogen drop in the hypothalamic ascorbic acid concentration. Both doses of cimetidine potentiated the growth reaction of the adenohypophysis to oestrogens, but did not affect the blood polyphenol oxidase, the hypothalamic polyphenol oxidase or the hypothalamic ascorbic acid reaction. If administered alone, the larger dose of cimetidine mildly reduced serum polyphenol oxidase [ceruloplasmin] activity.