DISCUSSION 



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DISCUSSION 



Dr. Loutit: If we score our protective action versus the dose of 5-hydroxytryptamine 

 employed, I understand that Dr. van den Brenk got a linear rise with molarity of 

 5-hydroxytryptamine, whereas Hope's data certainly goes through a maximum and 

 then decreases with increasing molarity. On the other hand he did also score body 

 temperature and found that body temperature fell with increasing dose. Tlius there 

 was this divorcement of protective action and body temperature. Have you any 

 commentary on that sort of observation ? 



Mr. van den Brenk : With the doses of 5-hydroxytryptamine that we used we do get 

 a linear relationship for a confined range of dosage. I have only increased the dose 

 (this is in rats) up to 7-5 [xmoles after which I found that a lot of the animals died 

 early as a result of the injection which was thus getting on towards the maximum 

 tolerated dose of about 7 ■ 5 ijimoles. Beyond this level of dosage I have no information. 

 With regard to hypothermia — I doubt if that is an important factor in 5-hydroxy- 

 tryptamine protection because reserpinized rats are definitely more hypothermic 

 than rats treated with 5-hydroxytryptamine but fail to show significant radio-protective 

 effect, despite being completely tranquillized, and their body temperature thus even 

 lower. 



Dr. Vogel: Several years ago I believe there was a report by von Sallmann at 

 Columbia which stated that there was some protection in the epithelium of the lens, 

 for cysteine as judged by mitotic counts and in the reduction in cataracts formed 

 after whole-body irradiation with X-rays. I wondered if, with any of the agents that 



177 



