PLASMA AND URINARY PLATELET-ACTIVATING-FACTOR CONCENTRATIONS AND LEUKOTRIENE RELEASING ACTIVITY OF LEUKOCYTES IN STEROID SENSITIVE NEPHROTIC SYNDROME OF CHILDHOOD

Platelet activating factor (PAF) is synthesized and secreted by glomer ular mesangial and endothelial cells. It increases glomerular basement membrane permeability and induces proteinuria. Leukotrienes (LT) are mediators released by either leukocytes or glomerular cells under the PAF effect. The possible role of PAF in steroid sensitive nephrotic sy ndrome (SSNS) of childhood was studied in 8 children with SSNS in the acute stage, 5 children in remission and 8 healthy controls. The PAF c oncentrations in urine and plasma were determined. Leukocytes were sti mulated in vitro and the LT release in response to stimulation was det ermined. The urinary and plasma concentrations of PAF were significant ly higher in the acute phase than in remission and in control patients . Children with SSNS were found to have peripheral leukocytes with inc reased LT releasing activity in vitro. These results are in accordance with clinical and experimental observations indicating that PAF origi nates in the kidney and plays a role in normal kidney physiology. Urin ary PAF concentrations may be related to proteinuria because they were strongly correlated in the present study. Elevated plasma PAF concent rations in the acute stage of SSNS could result from either its secret ion from the circulating leukocytes or decreased acetyl hidrolase acti vity needed for its hydrolysis in plasma. The increased LT release in vitro suggests that these cells might have been activated by PAF secre ted from glomeruli. It is proposed that PAF and different LT in system ic and glomerular circulation are important mediators in childhood SSN S.