Ornithine decarboxylase activity in rat liver during phalloidin poisoning.

Rat liver ornithine decarboxylase activity was measured during phalloidin poisoning of 17 day-old rats, adult rats, and adult rats protected against phalloidin toxicity by pretreatment with somatotropin. The results show: 1. In adult rats, after a short period of activation, ornithine decarboxylase activity decreases to basal levels after phalloidin administration and remains so until death. 2. In somatotropin-pretreated rats, the enzyme activity increases with a peak 4 hours after injection of somatotropin but then drops rapidly to control levels. All rats survive poisoning. In somatotropin-pretreated rats that has also been given the ornithine decarboxylase inhibitor, 1,3-diaminopropane, phalloidin poisoning causes a decrease in the enzyme activity to basal levels and death of all animals. 3. In 17 day-old rats, ornithine decarboxylase activity decreased initially after phalloidin poisoning but then returned to unpoisoned levels. All rats survived poisoning, even those pretreated with 1,3-diaminopropane.