The high yield of prostacyclin biosynthesis by the iris and its effects on the intraocular muscles

Abstract Iris, and to a lesser extent ciliary body , from cat and rabbit produce considerable amounts of prostacyclin (PGI 2 ) after incubation of the tissue with 1- 14 C arachidonic acid. These tissues also generate PGI 2 -like material after gentle squeezing. It is likely that major metabolites found previously in iris and aqueous humor actually were 6-keto-PGF 1α . It is concluded that PGH 2 and PGI 2 are synthetized at the same location. PGI 2 induces a contraction of the sphincter and dilator and a relaxation of the ciliary muscle if the tissues had been previously exposed to indomethacin. Thromboxane A 2 (TXA 2 ) has either no effect or may cause a slight relaxation of the sphincter.