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Regulation and bioelectrical effects of cyclic adenosine monophosphate production in the ciliary epithelial bilayer.

Abstract：

PURPOSE:To determine whether the intact isolated ciliary epithelial bilayer retains the alpha-2 and beta adrenergic receptor activation and interaction described for whole ciliary processes and whether this pure epithelial bilayer displays bioelectric parameters sensitive to alterations in cyclic adenosine Monophosphate (cAMP) production induced by adrenergic compounds. METHODS:The intact ciliary epithelial bilayer of the rabbit eye isolated by perfusion was mounted in a specially constructed Ussing-type chamber. The transepithelial potential difference and short-circuit current were monitored for effects induced by agents that stimulated or blocked (some did both) caMP production. Using a radioimmunoassay, the latter were studied in the pure epithelial bilayers and in whole ciliary processes. RESULTS:A reproducible increase in cAMP production and an increase in the short-circuit current induced in the bilayer by isoproterenol, a nonspecific beta adrenergic agonist, were both blocked by pretreatment with either timolol, a nonspecific beta adrenergic blocking agent, or with para-aminoclonidine, an alpha-2 agonist. Maximal stimulation of cAMP with forskolin in this pure isolated epithelial preparation yields a response that is 60% of the value found in whole processes, indicating that the latter tissue contains responsive sites that are nonepithelial, probably vascular, or perhaps stromal. The degree of inhibition of the beta adrenergic receptor by alpha-2 agonists was not very different in the two preparations. On the other hand, inhibition of the epithelial vasointestinal peptide receptor by neuropeptide Y or alpha-2 agonism was considerably heightened in the pure bilayered epithelial preparation. CONCLUSIONS:The isolated intact ciliary epithelial bilayer, when stimulated with beta adrenergic receptor agonists, vasointestinal peptide, or forskolin, produces increased cAMP and its transepithelial potential becomes hyperpolarized. These chemical and bioelectrical effects are prevented by pretreatment with either alpha-2 adrenergic agonists or beta adrenergic blocking agents. The results obtained in the isolated intact purely epithelial ciliary bilayer confirm that the ciliary epithelium is the source of adrenergic receptor activation and interaction and support the hypothesis that aqueous humor production is regulated by interactions between epithelial alpha-2 and beta adrenergic receptors.

journal_name

Invest Ophthalmol Vis Sci

journal_title

Investigative ophthalmology & visual science

authors

Horio B,Sears M,Mead A,Matsui H,Bausher L

subject

Has Abstract

pub_date

1996-03-01 00:00:00

pages

607-12

issue

eissn

0146-0404

issn

1552-5783

journal_volume

pub_type

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Regulation and bioelectrical effects of cyclic adenosine monophosphate production in the ciliary epithelial bilayer.