Alterations in the activities of ornithine and histidine decarboxylases provoked by testosterone in mice.

1. The urinary excretion of putrescine has been determined in female mice before and during repeated injections of testosterone.2. Testosterone administration effected a striking increase in the excretion of free putrescine.3. Ornithine decarboxylase (L-ornithine carboxy-lyase; E.C. 4.1.1.17) and histidine decarboxylase (L-histidine carboxy-lyase; E.C. 4.1.1.22) activities of mouse kidney and liver were examined. In the kidney, following testosterone administration, ornithine decarboxylase activity was found to be substantially elevated, whereas that of histidine decarboxylase was depressed. In the liver, by contrast, the activity levels of these enzymes were not significantly altered by testosterone treatment.4. The possibility of a functional interrelation between putrescine and histamine, via the two enzyme activities investigated, is discussed.