The objective of this proposal is to learn the cellular and molecular characteristics of the transporting systems for aqueous secretion by studying transepithelial transport across the ciliary epithelium of the eye. A completely new sort of membrane preparation of the isolated bilayered ciliary epithelium has been developed to facilitate these studies. Studies of this bilayer would be compared to single layer preparations of the pigmented and non-pigmented epithelium that have also been obtained. The bioelectric characteristics of this preparation, the transepithelial potential difference, resistance and short circuit current would be determined. Electrical and tracer methods would be used to examine the mechanisms for ion permeation. For example, the separate contributions of sodium, chloride and bicarbonate to the net current across these cellular preparations and their interactions would be studied. What fractions of the short circuit current are accounted for by the separate ions? The likelihood of electrically silent pathways would then be explored. Is the response polarized? The nature of these different transport processes would be examined and quantified. What is the involvement of channel mechanisms and/or carrier-mediated processes? The characteristics of potentially important outward anion transport (kidney and liver-like) systems can and would be determined in this preparation. The preparation would be used to explore how these transporting systems are regulated. Extracellular regulatory pathways would be examined by activating appropriate receptors with neurohormones, mediators and local hormones or neuropeptides to learn the potential role of these substances in influencing secretion. In particular the cyclic nucleotide messenger system would be explored to learn its functional relationship to the vectorial transport pathways for ions. It is also planned to study the transfer of ascorbic acid and glucose. Data obtained from certain kinetic studies of transport would be modeled to several kinetic analyses and compared with past uptake studies when possible. The rate of aqueous humor formation and its composition determine the nutrition of the avascular parts of the eye; the interior cornea, the trabecular meshwork, crystalline lens and probably the anterior vitreous. Therefore this research would bear on certain corneal dystrophies, glaucoma, possibly cataract, and changes in the vitreous with age. Studies of drug mechanisms, e.g., beta adrenergic blockers, would improve the applicant's understanding of the intrinsic mechanisms of aqueous humor formation and help determine how these agents reduce aqueous flow in glaucoma.
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