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Haruna Suzuki-Kerr, Julie C. Lim, Paul J. Donaldson; Purinergic Receptors in the Rat Lens: Activation of P2X Receptors following Hyperosmotic Stress. Invest. Ophthalmol. Vis. Sci. 2010;51(8):4156-4163. doi: 10.1167/iovs.09-5023.
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A range of P2Y and P2X receptors is expressed in the rat lens. Because most P2X receptors are located in the cytoplasm, the authors sought to determine whether P2X receptors are functionally active.
Rat lenses were cultured under either isotonic or hypertonic conditions in the presence of P2 receptor agonists or antagonists. Lenses were fixed and cryosectioned, cell membranes were labeled, and confocal microscopy was used to determine whether the different reagents affected cell morphology.
Application of the P2 receptor inhibitor PPADS to lenses cultured under isotonic conditions induced extracellular space dilations between fiber cells in a distinct zone in the outer cortex. This damage was not caused by the inhibition of P2X1 or P2Y1 because more selective antagonists for P2X1 (MRS2159) and P2Y1 (MRS2179) either did not cause any damage or induced extracellular dilations located between superficial fiber cells at the lens modiolus, respectively. Although the P2 agonists ATPγS and ADPβS both induced a distinctive disruption to cell morphology in the same localized zone as PPADS, the P2X-specific agonist α,β-methyl-ATP induced no change to cell morphology. However, under hypertonic conditions that cause the insertion of P2X1,4 into the membranes, α,β-methyl-ATP induced a localized zone of damage that was associated with changes in actin distribution.
The results show that P2X receptors may play a minimal role in mediating ion fluxes in the rat lens under steady state conditions. In contrast, hypertonic cell shrinkage activates previously inactive P2X receptors in the lens, suggesting P2X receptors may play a role in the lens in response to osmotic stress.
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