Histamine metabolism and pinnal hyperaemia during magnesium deficiency in rats

The relation between histamine metabolism and an appearance of pinnal hyperaemia during magnesium (Mg) deficiency, and the effects of some factors on these were studied in 3-week-old Wistar rats. On a Mg-deficient diet (Mg 0.001%), the histamine concentrations in plasma and urine increased after 4-5 d, and reached a maximum after 6-12 d. Pinnal hyperaemia appeared during the same time course. The hyperaemia was reduced by the administration of antihistamines (cimetidine and diphenhydramine). These results indicate that pinnal hyperaemia during Mg deficiency is mediated by histamine. The administration of oestradiol benzoate (0.08 mg/100g body weight subcutaneously once a day for 8 d) and/or gamma-ray irradiation (600 rad/d before experiments) reduced the appearance of pinnal hyperaemia and the increment in the urinary histamine during Mg deficiency. The histamine content increased in the spleen and some tissues after 8 d, but not in the skin, with increasing the activity of histamine synthesis. The treatments mentioned above depressed the increment of histamine content. These results suggest that the pinnal hyperaemia and the increment of the urinary histamine in the Mg-deficient rat are related to the increment of both the histamine synthesis and release.