[Mediation of the lithium increase in rat liver tryptophan pyrrolase activity by 11-hydroxycorticosteroids].

After a single intraperitoneal administration lithium carbonate (50 and 100 mg per kg of body weight) caused an increase in the tryptophane pyrrolase activity in rat liver tissue by 50-80% within 5 hrs and did not affect the enzyme within 1, 3 and 20 hrs. Content of lithium was quite unaltered in rat blood serum after administration of lithium carbonate at a dose of 50 mg/kg; it slightly exceeded the therapeutic level at a dose of 100 mg/kg. Addition of the lithium preparation (7-10(-3)-7-10(-5) M) to liver homogenates did not change the tryptophane pyrrolase activity in vitro. The same doses of lithium (50 and 100 mg/kg) caused a 2.5-fold increase in content of 11-hydrocorticosteroids in rat blood plasma; the effect was prevented by previous administration of dexamethasone. In experiments with adrenalectomized rats lithium did not affect the enzymatic activity. Repeated administration of lithium (50 mg/kg) within 10 days did not affect the tryptophane pyrrolase activity and did not alter the content of 11-hydroxycorticosteroids in rat blood plasma. The data obtained suggest that the increase in the tryptophane pyrrolase activity, caused by lithium, is mediated through the elevation in content of 11-hydroxycorticosteroids in blood.