Increased concentrations of phosphatidylinositol (PI) and decreased esterification of arachidonic acid into phospholipids in platelets from patients with schizoaffective disorders or atypic phasic psychoses.

The concentration of various phospholipids (PLs) and sphingomyelin in platelets and the amount of [14C] arachidonic acid ([14C]-AA) esterified in phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine (PE), and phosphatidylcholine (PC) were measured. The platelet-rich plasmas from unmedicated patients with psychiatric disorders and healthy controls were incubated for 30 min with 1 microM [14C]-AA. Platelets from patients with a schizoaffective disorder according to RDC criteria, a schizophreniform disorder (DSM III criteria) or an atypical phasic psychosis according to FC criteria contained twice as much PI and had significantly increased concentrations of PC as compared to controls (p less than 0.05, t-test). A highly significant (40-70%) reduced rate of esterification of [14C]-AA into PI/PS, PC and PE was found in platelets from patients with schizophreniform, schizoaffective and major depressive disorders but not in platelets from patients with chronic schizophrenia. The largest reduced esterification of [14C]-AA (about 70%) was found in PI/PS of platelets from patients with schizoaffective disorders (1.9 +/- 0.7 vs 6.3 +/- 1.7 mumol [14C]-AA/mol PI/PS; p less than 10(-4), t-test). The results indicate that changes in the metabolism of arachidonic acid and phosphatidylinositol and, to a lesser degree, of phosphatidylcholine in platelets are characteristic of patients with a likely favorable outcome of a psychotic episode.