THE RESPONSE OF NORMAL, HYPOPHYSECTOMISED AND ADRENALECTOMISED RATS TO HISTAMINE ADMINISTRATION

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Abstract
The toxicity of single sub-cut, injs. of histamine was studied in normal, adrenalec-tomised and hypophysectomised rats. Treatment of hypophysectomised rats with corticotrophic hormone greatly increased their lowered resistance to histamine, but desoxycorticosterone had no effect. Adrenalectomised rate maintained on oral saline had a low tolerance to histamine but this was raised in some instances by desoxycorticosterone. Hb detns. showed that in normal rats hemoconc. was maximal 30 mins. after histamine. Dilution of the blood occurred rapidly and reached normal levels by 6 hrs., but further dilution took place up to 24 hrs. In hypophysectomised and adrenalectomised rate, the changes in Hb were all exaggerated and more prolonged. When the former rate were treated with a corticotrophic extract affording protection the Hb changes resembled those found for normal rather than for hypophysectomised animals. Pqlydipsia occurred in normal animals for the 1st hr. after histamine and polyuria was always present in the first 24 hrs. A comparable polyuria was never found in hypophysectomised rats after histamine, possibly related to the inability of the hypophysectomised rat to develop polyuria following the ingestion or inj. of water. Corticotrophic hormone did not restore this derangement in water excretion.