Effect of sex steroids on tryptophan and carbohydrate metabolism in female rats

ABSTRACT

The activities of L-tryptophan 2, 3-dioxygenase [EC 1. 13. 11. 11], pyridoxal phosphokinase [EC 2. 7. 1. 35], kynurenine transaminase [EC 2. 6. 17] and kynurenine hydrolase [EC 3. 7. 1. 2] were determined in female rats, following two weeks of sex steroid administration, to assess their effect on tryptophan metabolism. Steroid effect is also studied on carbohydrate metabolism, through an evaluation of blood glucose, liver glycogen and serum cortisol levels. Administration of testosterone propionate [TP] and combination of ethinyl estradiol plus progesterone [EE+P], resulted in a significant decrease in the activity of L-tryptophan 2, 3-dioxygenase. Pyridoxal phosphokinase was significantly inhibited by [TP], while [EE+P] caused a significant increase in its activity, [TP] and [EE+P] produced an inhibitory effect on kynurenine transaminase and kynurenine hydrolase. Liver glycogen content was significantly increased by [TP] and [EE+P], while blood glucose level and serum cortisol concentration were not changed significantly. In conclusion, male and female hormones produce a disorder in tryptophan metabolism. Some abnormalities in carbohydrate metabolism are also observed