FATTY-ACID COMPOSITION OF THE MAJOR PHOSPHOLIPIDS OF PNEUMOCYSTIS-CARINII CARINII - COMPARISON WITH THOSE IN THE LUNGS OF NORMAL AND METHYLPREDNISOLONE-IMMUNOSUPPRESSED RATS

Large numbers of viable organisms can be isolated from the corticoster oid-immunosuppressed rat model of Pneumocystis carinii pneumonia, With the development of purification protocols that provide organism prepa rations of high purity, meaningful lipid biochemical analyses of this important opportunistic pathogen can now be conducted, The phospholipi d class composition of the pathogen was reported earlier, together wit h observations of changes that occur in the rat lungs in response to m ethylprednisolone immunosuppression treatment. In this report, analyse s of the effects of corticosteroids on the fatty acid compositions of the major lung phospholipids, individually isolated and purified by th in-layer chromatography, were elucidated and quantified by gas-liquid chromatography. In response to methylprednisolone, there was a relativ e increase in palmitate and there were decreases in several unsaturate d fatty acids of the rat whole-lung total polar lipids, leading to a d oubling of the saturation index. Reciprocal changes in the relative co ncentrations of palmitate and stearate in phosphatidylethanolamine, ph osphatidylinositol, lysophosphatidylcholine, and cardiolipin were obse rved, suggesting that there is tight control of acylation of these pho spholipids in the lung. Detailed phospholipid fatty acid analyses were also performed with mixed life cycle stages of P. carinii organisms. The most abundant phospholipids, phosphatidylcholine, phosphatidyletha nolamine, and phosphatidylinositol, had much higher concentrations of oleic acid and lower concentrations of palmitate in P. carinii than in lung tissue, Sphingomyelin in lung tissue and P. carinii differed fro m the glycerophospholipids by the presence of high levels of saturated C-22 and C-24 fatty acids. This study represents the most comprehensi ve fatty acid analysis of rat lung phospholipids and the changes that occur in response to corticosteroid treatment. It is the first report about the fatty acids of individual phospholipids of the opportunistic protist P. carinii carinii.