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. 2002 Mar;119(3):251–273. doi: 10.1085/jgp.20028537

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Copyright © 2002, The Rockefeller University Press

This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).

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Figure 6. — The location of polar groups in the side of the steroid nucleus opposite to where the hydrophobic methyl groups are located favors the activation of BK_Ca channels by bile acids. For each panel, records of channel activity in inside-out patches in the absence and presence of a given bile acid analogue (100 μM) are shown on the right. A shorthand representation of the analogue applied is on the left. In the representations, the dotted line crossing these bean-shaped molecules illustrates the equatorial plane, and black circles correspond to polar groups (whether hydroxyls or carboxyls). The lateral chain and the methylenes of the hemisuccinate are depicted as zig-zag lines. For lithocholic acid, the Stuart-Briegleb space filling model also is shown at the top of the corresponding shorthand representation. (A) Lithocholic acid rapidly increases BK_Ca channel activity (top trace), whereas ursocholanic acid, which does not have any hydroxyl groups (middle trace), or the β-isomer of lithocholic acid (bottom trace) fail to do so. The top and middle records were obtained in the same patch, with the patch potential set to +30 mV. The bottom record was obtained with the patch potential set to +40 mV. (B) Either “7,12 deoxycholic acid” (top trace) or lithocholic acid 3-hemisuccinate (bottom trace) reversibly increase BK_Ca channel activity. These two compounds do not have a hydroxyl in the α configuration at C3, but still possess polar groups (whether hydroxyls or a bulky hemisuccinate) in the axial plane of the molecule, opposite to the hydrophobic side of the steroid plane (see Fig. 1 and models of these analogues on the left of each record). The patch potential was set to +50 and +30 mV.

Figure 6. — The location of polar groups in the side of the steroid nucleus opposite to where the hydrophobic methyl groups are located favors the activation of BK_Ca channels by bile acids. For each panel, records of channel activity in inside-out patches in the absence and presence of a given bile acid analogue (100 μM) are shown on the right. A shorthand representation of the analogue applied is on the left. In the representations, the dotted line crossing these bean-shaped molecules illustrates the equatorial plane, and black circles correspond to polar groups (whether hydroxyls or carboxyls). The lateral chain and the methylenes of the hemisuccinate are depicted as zig-zag lines. For lithocholic acid, the Stuart-Briegleb space filling model also is shown at the top of the corresponding shorthand representation. (A) Lithocholic acid rapidly increases BK_Ca channel activity (top trace), whereas ursocholanic acid, which does not have any hydroxyl groups (middle trace), or the β-isomer of lithocholic acid (bottom trace) fail to do so. The top and middle records were obtained in the same patch, with the patch potential set to +30 mV. The bottom record was obtained with the patch potential set to +40 mV. (B) Either “7,12 deoxycholic acid” (top trace) or lithocholic acid 3-hemisuccinate (bottom trace) reversibly increase BK_Ca channel activity. These two compounds do not have a hydroxyl in the α configuration at C3, but still possess polar groups (whether hydroxyls or a bulky hemisuccinate) in the axial plane of the molecule, opposite to the hydrophobic side of the steroid plane (see Fig. 1 and models of these analogues on the left of each record). The patch potential was set to +50 and +30 mV.