Urinary excretion of platelet-activating factor in human and experimental nephrosis

Platelet-activating factor (PAF) is a phospholipid that has been implicated in the pathogenesis of glomerulonephritis and can be synthesized by glomerular cells in response to different stimuli. PAF increases glomerular permeability to proteins and urinary PAF has been determined to be of renal origin. In order to assess whether urinary PAF can be found augmented in situations of glomerular damage without glomerular leukocyte infiltration, urinary PAF was quantified in human and experimental nephrosis.

Urinary PAF was quantified by platelet bioassay and glomerular PAF by incorporation of 3H-acetate into PAF. PAF was characterized by its behaviour on thin-layer chromatography and high performance liquid chromatography and the blockade of its bioactivity by receptor antagonists.

Urinary PAF excretion was significantly higher in patients with active idiopathic nephrotic syndrome than in controls (5.8+/-1.5 versus 1.7+/-0.75 mg/24 h; P<0.05) and patients in remission (1.63+/-0.75 ng/24 h; P<0.02). In rats with nephrosis induced by puromycin aminonucleoside there was an early increase in urinary PAF excretion (138+/-19 versus 49+/-22 pg/24 h in controls; P<0.035) that coincided with the augmented glomerular PAF synthesis (67+/-3.4 versus 36+/-1.2 DPM/mg protein in controls; P<0.003).

These results suggest that the synthesis of PAF in the kidney may be involved in the pathogenesis of the proteinuria in idiopathic nephrotic syndrome and that urinary PAF excretion may be a good marker of disease activity.