Brain tryptophan uptake and sodium-potassium ATPase activity in long-term streptozotocin diabetic rats.

Serum, liver and brain tryptophan concentrations and brain Na+K(+)-ATPase activity were studied in streptozotocin diabetic rats after an acute tryptophan load. Results show that tryptophan administration in the experimental diabetic group produces a generalized fall in tryptophan uptake in all the brain regions studied, though it does not increase serum and hepatic tryptophan concentrations. These parameters are normalized in insulin-treated diabetic rats. With regard to Na+K(+)-ATPase, diabetic animals showed a diminished and unchanged activity; whereas, the other two experimental groups showed a gradual decrease and a negative correlation with brain tryptophan uptake.