Renal effects of platelet-activating factor in the rat

The renal glomerular and tubular effects of the platelet-activating factor (Paf-acether) were studied, by clearance techniques, in acutely thyroparathyroidectomized Brattleboro rats infused with Paf-acether at the rate of 1.25, 2.5 or 5 ng/min/100 g bw. Paf-acether infusion was accompanied by decreases of urinary flow rate, calcium, and magnesium urinary excretion, whereas decreases of mean arterial pressure and glomerular filtration rate did not exceed 20% of control values for the highest perfusion rate of Paf-acether. These changes in tubular function were partially (calcium excretion) or totally (urinary flow rate and magnesium excretion) reversed after Paf-acether infusion was discontinued. Sodium and potassium excretion did not vary significantly during Paf-acether infusion, but increased dramatically after discontinuation of Paf-acether infusion. Infusion of lyso-Paf-acether or ethoxy-Paf-acether, two biologically less active structural analogues of Paf-acether, did not elicit any change in the variables studied. These data suggest that Paf-acether, when locally released by the kidney in pathological conditions, might affect both glomerular and tubular functions, possibly through different mechanisms.