1. The prostaglandin precursor arachidonic acid (C20:4) increases plasma renin activity in the rabbit and rat when it is infused into the renal arteries.
2. The increase in plasma renin activity after C20:4 in rats is not changed by volume expansion.
3. The inhibitor of prostaglandin synthesis indomethacin decreases plasma renin activity in the rabbit.
4. The increase in plasma renin activity after total renal ischaemia is abolished by pretreatment with indomethacin.
5. C20:4 increases dose- and time-dependent renin release from slices of rabbit kidney cortex.
6. Indomethacin or 5,8,11,14-eicosatetraynoic acid pretreatment in vivo, and addition to the incubation medium, reduces basal as well as C20:4-stimulated renin release in vitro.
7. The stimulating effect of C20:4 on renin release is assumed to be caused directly by formation of prostaglandin endoperoxides in the kidney cortex and not by prostaglandins since in vitro a natural prostaglandin endoperoxide (PGG2) and two stable synthetic prostaglandin endoperoxide analogues (EPA I and EPA II) do increase the release of renin, but PGE2 has no effect and PGF2α inhibits renin release.