We propose to study the roles of cGMP and cGMP-mediated transmitters in regulating ciliary epithelial function. On a systemic level, the natriuretic peptides (ANP and BNP) and NO on the one hand, and angiotensin II (AII) on the other, form a pair of balancing and opposing transmitters regulating vasomotion; the natriuretic peptides and AII also oppose each other in regulating natriuresis. This integrative balance is partly mediated through changes in the intracellular concentration of cGMP (cyclic guanosine-3',5'-monophosphate), which is increased by natriuretic peptides and NO and decreased by AII. Published data indicate that the ciliary epithelium can respond and/or has receptors to all of these transmitters. Furthermore, on an intracellular level, the two cyclic nucleotides cGMP and cAMP (cyclic adenosine-3',5'-monophosphate) appear to constitute an additional pair of balancing and opposing messengers, regulating the secretion of aqueous humor. On the basis of published data and our unpublished observations, we have formulated a hypothesis concerning the roles of cGMP in regulating the rate of aqueous humor secretion. We propose that the major effect of cGMP is to reverse a cAMP- mediated inhibition of the Na,K-exchange pump, involving both protein kinase A and DARPP-32 of the non-pigmented ciliary epithelial cells. The experimental approach of the current program will be to measure both transepithelial and transmembrane transport by the ciliary epithelium. We shall perform transepithelial measurements and cell-attached patch clamping of the intact ciliary epithelium from both the rabbit (whose characteristics have been well defined) and the cat (whose properties are likely closer to those of primates). We shall also study primary and/or continuous lines of non-pigmented and pigmented ciliary epithelial cells (of human, bovine, rabbit and cat origin) by patch clamping in the conventional whole-cell, perforated whole-cell, cell-attached and excised- patch modes. The specific objectives of the research program are to: (1) determine the effects of each transmitter (ANP, BNP, AII, and NO) separately, and the interactions of these transmitters; (2) test whether the interactions between the transmitters and second messengers (cGMP and cAMP), and between cAMP and cGMP themselves, conform to the hypothesis proposed; and (3) determine whether the cyclic nucleotide-regulated effects are mediated by the transport mechanisms postulated.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY010691-02
Application #
2164734
Study Section
Visual Sciences A Study Section (VISA)
Project Start
1994-08-01
Project End
1998-07-31
Budget Start
1995-08-01
Budget End
1996-07-31
Support Year
2
Fiscal Year
1995
Total Cost
Indirect Cost
Name
University of Pennsylvania
Department
Physiology
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
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Mitchell, C H; Peterson-Yantorno, K; Carre, D A et al. (1999) A3 adenosine receptors regulate Cl- channels of nonpigmented ciliary epithelial cells. Am J Physiol 276:C659-66
Civan, M M; Peterson-Yantorno, K; Sanchez-Torres, J et al. (1997) Potential contribution of epithelial Na+ channel to net secretion of aqueous humor. J Exp Zool 279:498-503
Carre, D A; Mitchell, C H; Peterson-Yantorno, K et al. (1997) Adenosine stimulates Cl- channels of nonpigmented ciliary epithelial cells. Am J Physiol 273:C1354-61
Jacob, T J; Civan, M M (1996) Role of ion channels in aqueous humor formation. Am J Physiol 271:C703-20
Chalfant, M L; Peterson-Yantorno, K; O'Brien, T G et al. (1996) Regulation of epithelial Na+ channels from M-1 cortical collecting duct cells. Am J Physiol 271:F861-70
Chalfant, M L; O'Brien, T G; Civan, M M (1996) Whole cell and unitary amiloride-sensitive sodium currents in M-1 mouse cortical collecting duct cells. Am J Physiol 270:C998-1010
Carre, D A; Civan, M M (1995) cGMP modulates transport across the ciliary epithelium. J Membr Biol 146:293-305