Cholinergic stimulation of vascular prostacyclin synthesis

The production of prostacyclin by rings of rabbit aorta was assessed by the radioimmunoassay of 6-keto-PGF1 alpha. In steady-state conditions, the rings released 11 ng 6-K-PGF1 alpha per 100 mg tissue in 30 min. Acetylcholine increased this output: a significant effect was detected at 1 microM and at 10 microM the amplitude of stimulation was 10-fold. The production of PGE2 and PGF2 alpha was also increased, but to a lesser extent. The stimulatory action of acetylcholine was mimicked by carbamylcholine and inhibited by atropine; it was abolished in a calcium-free medium. Dog and rat aorta also produced more 6-K-PGF1 alpha in response to cholinergic agonists. A short rubbing of the intimal surface of the aorta removed the layer of endothelial cells and completely abolished the cholinergic effect. It is concluded that in the aorta, cholinergic agonists, acting on a muscarinic receptor, stimulate the production of prostacyclin by endothelial cells.