Insulin-activated amiloride-blockable nonselective cation and Na+ channels in the fetal distal lung epithelium

• 1.1. The apical membrane of fetal distal lung epithelium had two types of amiloride-blockable Na⁺-permeant cation channels; (1) nonselective cation (NSC) channel with a single channel conductance of 27 pS and (2) Na⁺ channel with a single channel conductance of 12 pS around resting membrane potential.
• 2.2. The IC₅₀ of amiloride to the Na⁺ channel was 1–2 μM, while the IC₅₀ of amiloride to the NSC channel was less 1μM. The open probability of the Na⁺ channel was about 10-fold larger than that of the NSC channel.
• 3.3. Insulin (100 nM) increased the open probability of both channels.