ATRIOPEPTIN LOWERS AQUEOUS-HUMOR FORMATION AND INTRAOCULAR-PRESSURE AND ELEVATES CILIARY CYCLIC-GMP BUT LACKS UVEAL VASCULAR EFFECTS IN THEBOVINE PERFUSED EYE

The effects of atriopeptin (AP) on intraocular pressure (IOP), aqueous humor formation (AHF) and ciliary cyclic GMP in bovine eyes perfused in vitro through a ciliary artery were investigated. AHF was monitored fluorophotometrically by perfusing the anterior chamber with Barany's mock aqueous humor containing fluorescein. To study the effect of AP on cyclic GMP synthesis, eyes were injected with an intra-arterial bol us of AP prior to dissection of the ciliary processes. For comparison, individual, ciliary processes, or isolated ciliary epithelial cells w ere incubated with AP. Cyclic GMP was extracted by homogenization, aqu eous partition and column chromatography, and measured by radioimmunoa ssay (RIA). Decreases in IOP or AHF were seen (similar to) 15 min afte r the injection of AP and persisted throughout a 60-80 min perfusion. Arterial perfusion pressure was not significantly altered by AP, even when vascular tone was raised by adding noradrenaline to the perfusate . In whole eyes, ciliary cyclic GMP increased in response to AP. Cycli c GMP in isolated ciliary processes, or cultured ciliary epithelial ce lls incubated with AP also increased. We conclude that the decrease in IOP in the bovine eye by AP is due to a reduction in AHF, which is in dependent of any vascular effect. Ciliary cycle GMP may be the intrace llular mediator involved.