Production of platelet-activating factor in glomeruli and cultured glomerular mesangial cells

Platelet-activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) results in contraction of isolated glomeruli and cultured mesangial cells and concomitantly causes release of arachidonic acid and prostaglandin E2 (PGE2) formation. The kidney and isolated glomeruli can also generate material that has PAF bioactivity. We therefore examined the capacity of isolated renal glomeruli and cultured glomerular mesangial cells from rats to form PAF. Both isolated glomeruli and cultured mesangial cells transformed 1-O-alkyl-2-lyso-sn-glycero-3-phosphocholine ([3H]lyso-PAF) into a labeled product comigrating both on thin-layer chromatography (TLC) and high-pressure liquid chromatography (HPLC) with authentic PAF. Using rabbit platelet aggregation as bioassay for PAF, we found that isolated glomeruli produced 4 +/- 2 pmol/mg glomerular protein of PAF-like material, and mesangial cells produced 30 +/- 8 pmol/mg cell protein when stimulated with A23187 (10(-5) M) for 30 min. The major species of the PAF material produced by mesangial cells was identified as 1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphocholine after HPLC separation, followed by fast atom bombardment and gas chromatography-mass spectrometry. These results show that glomerular mesangial cells can produce PAF, which could contribute locally to the regulation of glomerular function.