Effect of hydrocortisone on histidine decarboxylase activity in rat stomach.

Hydrocortisone-stimulated synthesis of histidine decarboxylase (EC 4.1.1.22) was studied in rat stomach. Single or daily administration of hydrocortisone increased the histidine decarboxylase activity but not the histamine content in the fundic glands of stomachs from fed and fasted rats with or without adrenalectomy, and also in those from adrenalectomized fasted rats with concomitant treatment with pirenzepine, an inhibitor of gastrin secretion. The increase in histidine decarboxylase activity was maximal at 2 h after the administration of hydrocortisone, and the activity had returned almost to the pretreatment level by 4h after the administration. Furthermore, the increase was not augmented by daily administration of hydrocortisone for 3 d. Cycloheximide prevented the increase in gastric histidine decarboxylase due to hydrocortisone. Rat fundic gland tissue was found to possess binding sites for [3H]glucocorticoids in the cytosol. These results suggest that hydrocortisone stimulates the de novo synthesis of histidine decarboxylase in the fundic gland of rat stomach, though the response is not mediated by changes in the gastrin level.