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. 2003 Mar 24;100(7):4322–4327. doi: 10.1073/pnas.0736323100

Figure 2.

Figure 2

Anion selectivity and ATP permeability of macula densa maxi channel. (A) Single-channel recording from inside-out patches. Shown are current traces in control Ringer's ([NaCl] = 135 mM) solution (Left), low Cl− Ringer's solution ([Cl−] = 24.5 mM) (Center), and 100 mM ATP solution (Right). The pipette solution always contained 146 mM Cl−. (Right) Note the presence of channel activity at negative voltages that represents inward current generated by ATP4− efflux. Arrowheads represent the closed level of channel current, and vertical arrows indicate the step pulse onset. The membrane potential (−Vp) is indicated beside each current trace. (B) Single-channel I-V curves obtained from inside-out patches from macula densa cells. (Left) I-V curves in Ringer's solution containing [NaCl] = 135 mM (n = 12), low Cl− (substituted with gluconate; n = 8), or N-methyl-d-glucamine (NMDG; Na+-free; n = 3). (Right) I-V curves in which the bath contained either control Ringer's solution ([NaCl] = 135 mM) or 100 mM ATP solution (n = 7). (C) Expanded trace of single-channel current, presented in A (Right Lower), recorded at −50 mV in 100 mM ATP solution.