Endogenous Histamine Excretion in the Rat as Influenced by X-Ray Irradiation and Compound 48/80

¹ From the Division of Pharmacology and Toxicology, Atomic Energy Project, School of Medicine, University of California, Los Angeles, California

Studies have been made on a spasmogen from rat urine. This material has been identified as histamine. It has been shown that both acute whole body x-ray irradiation and compound 48/80 significantly increase the quantity of endogenous urinary histamine. Endogenous histamine excretion in female rats is approximately 9–10 times greater than in male rats. Neither x-ray irradiation nor compound 48/80 elevate the amount of urinary histamine of the males to that of the female. Histamine liberation is of little or no importance insofar as lethality from acute whole body irradiation is concerned. The amount of histamine liberated by such irradiation is independent of radiation dosage within the range 600–1200 r. After radiation injury, significant levels of urinary histamine were detected only during the first 24 hours. Histamine depletion by chronic administration of compound 48/80 did not prevent further liberation of histamine by acute whole body irradiation. Irradiated animals are much more susceptible to the toxic effects of compound 48/80 than normal animals. Gonadectomy followed by -estradiol injection did not increase the output of urinary histamine in male rats. Similar treatment of female rats with testosterone did not reduce their urinary histamine output, but a reduction was observed 140 days after surgery. Administration of cortisone acetate to male rats did not increase their excretion of endogenous histamine. Inactivation of diamine oxidase with aminoguanidine had little or no effect on urinary histamine output in male rats, but caused a threefold increase in females. Further elevation in urinary histamine was produced by irradiation or compound 48/80.