Plasma renin substrate during lithium treatment.

Inspired from experiments in animals, plasma renin substrate was determined in patients given lithium treatment. In a longitudinal study, renin substrate was determined in 9 patients before the start of lithium treatment and at intervals during 3 months of treatment. In a transversal study, 18 patients on lithium treatment for 2--20 years were compared with 11 control persons. In the longitudinal study, plasma renin substrate values did not, during lithium treatment, deviate significantly from pretreatment values. In the transversal study, values in the lithium-treated patients did not differ significantly from values in the control group. There were no correlations between serum lithium concentrations and plasma renin substrate values. Our study indicates that plasma renin substrate remains unaffected by lithium treatment of manic-depressive patients.