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Yong S Lee, Minzhong Yu, Lihua Marmortein, Neal S Peachey, Alan D Marmorstein; Soluble Adenylyl cyclase (sAC) in the retinal pigment epithelium plays a role in generating the light peak of the electrooculogram.. Invest. Ophthalmol. Vis. Sci. 2014;55(13):403.
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Niemeyer and Steinberg (Vis. Res. 24:275-28, 1984) demonstrated that the amplitude of the light peak (LP) of the electrooculogram (EOG) is diminished by elevated pCO2. In many cells, sAC an enzyme that catalyzes the hydrolysis of ATP to cAMP functions as a bicarbonate sensor generating cAMP in response to HCO3-. In this study we set out to determine if sAC is expressed in RPE cells and whether it plays a role in generating the LP.
We used immunofluorescence to localize sAC expression in the mouse eye. Immunoprecipitation and western blot were used in conjunction with adenylyl cyclase assays to verify expression of sAC in RPE lysates. To determine the effect of sAC on the LP, we measured the LP using dc-electroretinography in mice treated with the sAC specific inhibitor KH7 or vehicle alone.
: Immunofluorescence staining suggested that sAC is broadly expressed in the eye with highest expression apparent in the ciliary body, corneal endothelium, retina, and RPE. Expression of sAC in the RPE was confirmed by western blot, and immunoprecipitation using anti-sAC antibodies. Adenylyl cyclase assays confirmed that a bicarbonate dependent adenylyl cyclase is expressed in RPE that is inhibited by KH7. Mice treated with KH7 exhibited a diminished LP in comparison to control mice treated with vehicle alone.
Our data demonstrate that sAC is expressed by the RPE and that it contributes to the generation of the LP. Further study will be necessary to determine how cAMP generated by sAC may be involved in the LP response as a role for cAMP in generating the LP has not previously been observed.
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