The release of prostaglandins and rabbit aorta contracting substance (RCS) from rabbit spleen and its antagonism by anti-inflammatory drugs

1. Slices of rabbit spleen generate rabbit aorta contracting substance (RCS) and a prostaglandin of the E series when they are vibrated or stirred.

2. The release of both substances is increased by arachidonic acid and inhibited by aspirin-like drugs.

3. When the spleen effluent containing RCS and prostaglandin E is incubated for a further 3 min, the prostaglandin concentration increases and the RCS concentration declines.

4. RCS may therefore be an unstable intermediate in the biosynthesis of prostaglandins.