Platelet protein kinase C alpha levels in drug-free and lithium-treated subjects with bipolar disorder.

Recent studies suggest that protein kinase C (PKC), particularly the alpha isoform, plays an important role in the action of lithium. There is, however, little evidence from patients with bipolar disorder (BD) to support this effect. The present investigation carried out comparative studies of PKC levels in platelets obtained from BD subjects including those with and without lithium treatment. All subjects met DSM-IV criteria for BD type I confirmed by structured interview (SCID-IV). Levels of PKC-alpha isoform in platelets from controls and from BD subjects were measured with immunoblotting analysis. No significant differences were found between controls, drug-free or lithium-treated BD subjects on membrane or cytosolic levels of PKC-alpha or in the membrane-to-cytosol ratio of this protein. The present study suggests that levels of PKC-alpha do not change in the peripheral tissues of BD subjects with or without lithium treatment.