EFFECTS OF PHOSPHOLIPIDS ON RENAL-FUNCTION

The effects of two classes of phospholipids (PL) on renal function hav e been studied. Bolus injections of 1 ng (10 pmol) of lysophosphatidyl choline (LPC) caused natriuresis and diuresis in rats. Natriuretic act ivity was eliminated by substituting unsaturated bonds in the 1-acyl g roup and by removing the choline group on the sn-3 position. Natriuret ic activity was not affected by substitution of 1-alkyl for 1-acyl gro ups. In the dog, LPC was natriuretic when given as a bolus of 3.0 mug/ kg or as a constant infusion at 5 ng/kg/min. To explore further the ef fect of alkyl PLs on renal function, a series of studies with platelet activating factor (PAF) was performed. PAF injected directly into the renal artery (IR) in bolus doses of 0.5-10 ng/kg caused renal vasodil ation that was blocked by a specific PAF receptor antagonist. This eff ect was not due to release of vasodilatory eicosanoids, dopamine, or n itric oxide (NO). PAF given IR as a continuous infusion at 2.5 ng/kg/m in attenuated the renal vasoconstrictor effects of angiotensin II and norepinephrine but not vasopressin. This effect to attenuate vasoconst riction was blocked by the NO inhibitor N-monomethyl-L-arginine. These studies using picomolar amounts of PL suggest a physiologic role for these compounds in control of renal function.