Sex Difference of Pinnal Hyperemia in Magnesium-Deficient Rats: Effects of Castration and Administration of Sex Hormone

In the course of studies on the effects of magnesium (Mg) depletion in the diet (0.001% Mg) on mature rats (10 week-old), it became apparent that females developed less hyperemia than males. In the females, the time of onset and severity of hyperemia were enhanced by castration, but not in the males. These data suggest that the development of hyperemia in Mg-deficient adult rats depends on the female sex hormone. The effects of administration of estradiol were examined, using immature rats (3 week-old), in relation to hyperemia and histamine metabolism. Two to 3 days after feeding young male and female rats a Mg-deficient diet, the pinnal hyperemia appeared in the same degree. The hyperemia was reduced by the administration of estradiol benzoate (0.04-0.08 mg/100 g body wt. per day, s.c.) every day. The increments in urinary histamine excretion, splenic histamine content and histidine decarboxylase activity during Mg-deficiency were markedly reduced by the administration of estradiol. The sex difference in the hyperemia which appeared upon Mg-depletion depends on the effects of the female hormone, estradiol, on histamine metabolism.