Xenbase Image ID: 121098

Figure 1. Effect of UV light on currents through RET channels activated by saturating and low concentrations of ligand. (A and B) Current in response to 0 to +50 mV potential steps in the presence of: (A) saturating (1 mM) cGMP, and (B) 2 μM cGMP. Cyclic GMP-dependent current amplitudes before UV and after cumulative doses of 4.91 and 9.82 × 109 photons · μm−2 were: for 1 mM cGMP: 2,110 ± 4, 980 ± 5, and 297 ± 9 pA; and for 2 μM cGMP: 7 ± 2, 22 ± 3, and 40 ± 4 pA. Note the difference in vertical scales for traces in A and B, which are from the same patch. (C) Effect of UV light on RET channel cGMP dose–response relation. The cGMP-activated current (I) divided by the maximal current in 1 mM cGMP before irradiation (Imax)is plotted as a function of cyclic GMP concentration on double logarithmic coordinates. Relations were measured before UV exposure (•), and after cumulative doses of 4.91 × 109 photons · μm−2 (□), and 9.82 × 109 photons · μm−2 (▵). The continuous curves show fits to the results using the Hill equation ( of the text). The Hill coefficient, h, and the apparent affinity, K1/2, were: before UV exposure, h = 1.85 and K1/2 = 70.2 μM; after 4.91 × 109 photons · μm−2, h = 0.97 and K1/2 = 125 μM; after 9.82 × 109 photons · μm−2, h = 0.53 and K1/2 = 149 μM. Results from same patch as in A and B. The patch was irradiated with 280 nm UV in the absence of cGMP. The light intensity at the patch was 1.96 × 108 photons · μm−2 · s−1. Image published in: Middendorf TR and Aldrich RW (2000) © 2000 The Rockefeller University Press. Creative Commons Attribution-NonCommercial-ShareAlike license Larger Image Printer Friendly View

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