Effect of Anterior Hypophysis Emulsion on Natural Resistance of Hypophysectomized and Normal Rats to Histamine Poisoning

Abstract

In previous work we studied the effect of partial and complete hypophysectomy in rats on the natural resistance to histamine poisoning and correlated the anatomical changes in the suprarenal gland with the variations in resistance. We noted that the natural resistance of completely hypophysectomized rats to histamine poisoning was depressed during a period of one to ten weeks after operation. The M.L.D. was one-fifth to one-third that for normal rats. This decrease in resistance, we found, was associated with involutional changes of the suprarenal gland, such as hemorrhage into or atrophy of the inner zones of the cortex. Rats in which the posterior lobe and a large portion of the anterior lobe were removed showed a similar drop in resistance and atrophic changes in the suprarenal cortex occurred, but where a large fragment of the anterior lobe remained no depression in resistance to histamine occurred and the suprarenal glands were normal. We concluded that the drop in natural resistance following hypophysectomy in the rat was probably secondary to the atrophic changes of the suprarenal cortex induced by the withdrawal of the adrenotropic hormone of the anterior lobe. In subsequent studies it was found that repeated injections of large amounts of suprarenal cortical hormone raised the natural resistance of totally hypophysectomized adult rats to histamine poisoning. In some instances the resistance was raised almost to the level of normal rats. This was particularly marked during the first 2 weeks after operation, the period during which the most severe depression in natural resistance occurs. The M.L.D. of histamine for hypophysectomized rats within 2 weeks after operation varied from 200 to 300 mg. per kg. of body weight. Hypophysectomized rats treated with cortical hormone for 6 days prior to the injection of histamine survived, in many instances, 800 mg. of histamine per kg. of body weight.