Effect of Endofhelin on Outflow Facility and Accommodation in the Monkey Eye In Vivo

The effect of the vasoactive peptide, endothelin, on facility -of outflow, accommodation, and pupil diameter was measured in the monkey eye in vivo. Endothelin increased the outflow facility 22-71% at approximate anterior chamber concentrations ranging from 10~1 0 -10~7 M. Endothelin-induced accommodation was modest but consistent and statistically significant ranging from 1.61 to a maximum of 2.43 diopters at 10~9 M and 10~7 M endothelin, respectively. No change in pupil diameter was noted with any of the administered doses. These data demonstrate an action of endothelin on outflow facility and, together with prior evidence indicating the presence of endothelin receptors on the ciliary muscle, suggest that, like cholinergic agonists, the observed effects of endothelin on outflow facility may be mediated, at least in part, through an action on the ciliary muscle. Invest Ophthalmol Vis Sci 32: [492][493][494][495]1991 Endothelins are a group of vasoconstrictor polypeptides which have recently been isolated from porcine aortic endothelial cells. 1 Effects of endothelin on the cardiovascular system are similar to those of angiotensin II, but endothelin is much more potent. Endothelin also contracts nonvascular smooth muscle. " 4 A recent report documented that endothelin causes a membrane voltage depolarization and an increase in intracellular calcium in cultured human ciliary muscle cells at a concentration about two orders of magnitude lower than acetylcholine. 5 This result points to a possible physiologic role for endothelin in the ciliary muscle. In this report, we describe the results of in vivo experiments that demonstrate endothelin-mediated effects on both the facility of outflow and accommodation. Materials and Methods Five female cynomolgus monkeys (Macaca fascicularis) whose weights ranged from 2-3 kg were used in this study. For each procedure, the monkey was From th