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Under pentobarbital anesthesia, adult male dogs were irradiated with 1,000R of X-rays to their heads, and the adrenocortical response to histamine was investigated. The secretory activity was determined by estimating 17-hydroxycorticosteroids (17-OHCS) in adrenal venous blood. One day after irradiation, an intravenous injection of histamine (0.5mg/ kg body weight) to irradiated animals increased considerably the secretion of 17-OHCS from the adrenal, but the response was significantly less than that in non-irradiated animals. Thirty days after exposure, irradiated animals responded to the injection of histamine and secreted an appreciably large amount of 17-OHCS. However, the responsiveness was still lower than normal. It appears from these results that the corticotrophic effect of 0.5 mg histamine/kg can be dimi nished considerably by pretreatment with head X-irradiation of 1,000 R, possibly due to a disturbed activity of the hypothalamic-pituitary axis. head X-irradiation; adrenocortical response to histamine; dogs

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The effect of methylenedianiline on testicular 17-oxosteroid secretion caused by pregnant mare serum (PMS) was evaluated by measurements of 17-oxosteroids in the spermatic vein blood of the dog. Testicular 17-oxosteroid secretion in dogs which received a single injection of PMS (2,000 per animal) into the saphenous vein increased markedly and reached the maximum within approximately 90 minutes after the injection; the increase in secretion tended to be maintained over 4 hours of observation.At the highest rate of secretion, an intravenous injection of methylenedianiline (20 or 60mg/kg) into these dogs brought about a rapid decline in the output of testicular 17-oxosteroids.The response was reversible. These results show that methylenedianiline can prevent the augmented secretion of testicular 17-oxosteroids caused by pregnant mare serum.Methylenedianiline has been shown to diminish the secretion of 17-hydroxycorticsteroids from the adrenal in dogs.1 In a previous work,2 we have demonstrated that the stimulating effect of human chorionic gonadotrophin (HCG) on testicular 17-oxosteroid secretion is inhibited by methylenedianiline. It appears that the effect of methylenedianiline depends on a direct inhibition of androgen biosynthesis in testicular tissue. In this paper, the effect of methylenedianiline on testicular 17-oxosteroid secretion in response to pregnant mare serum will be presented. EXPERIMENTAL METHODSAdult male mongrel dogs 8.7-18.1kg in weight were used. Spermatic vein cannulation.The cannulation was done by a slight modification of the technique3 previously described.The dogs were anesthetized with an intravenous injection of 25mg/kg sodium pentobarbital and maintained by supplement of the drug as required.Through a longitudinal incision in the left lumbar area, the left spermatic vein and left lumbo-adrenal vein were exposed, and after systemic administration of heparin, the vessels were connected to a T-shaped glass cannula fitted with a rubber tube, so that the blood from the testis could flow through the spermatic vein to the lumbo-adrenal vein during periods when blood was not being collected.

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