Endogenous Prostaglandin Synthesis Inhibitor in the Renal Cortex. Effects on Production of Prostacyclin by Renal Blood Vessels

1. The capacity of various tissues of the porcine kidney to convert [1-¹⁴C]arachidonic acid into radiolabelled prostaglandins was studied.

2. Only after removal from the cortical matrix, were renal blood vessels able to convert arachidonic acid into prostaglandins (primarily prostacyclin). In contrast, convoluted tubules showed a low capacity to metabolize arachidonic acid.

3. The failure to demonstrate prostaglandin synthesis by renal cortical slices is related to the presence of an inhibitor of cyclo-oxygenase. Thus, the addition of renal cortical incubate to isolated vascular tissues and ram seminal vesicles inhibited their ability to synthesize prostaglandins.

4. Slices of renal medulla metabolized arachidonic acid primarily to prostaglandin F_2α; lesser amounts of prostaglandin E₂ and prostacyclin were generated.

5. The large capacity of the renal vasculature to generate prostacyclin is consistent with an important role for this prostaglandin in regulation of renin release and renal haemodynamics.