Figure 5.

Amiloride sensitivity of αβγ Cys mutants. (A) Original tracings of amiloride inhibition of inward Li⁺current in oocytes expressing βG525C mutant together with α and γ subunits. Triangles (▴) represent addition of external amiloride at increasing concentrations of 0.1, 10, 70, and 100 μM, and • indicates return to the starting K solution. (B) Titration curve of Li⁺current by amiloride. I/I₀ is the ratio of blocked over unblocked Li⁺current. Li⁺ current was measured in individual oocytes in the presence of four different amiloride concentrations (wt-ENaC, n = 82; αS583C, n = 27; βG525C, n = 59; γG537C, n = 14) Dotted lines represent fit of data to a Langmuir inhibition isotherm (see materials and methods).