Fig. 2. Effects of apical Na⁺ channel blockers on basal I_sc. (A) Time course of I_sc inhibition following sequential treatment with 10 and 100 µmol l^-1 amiloride. (B) Concentration–response relationships for amiloride and benzamil on basal I_sc. The data was fitted using a four-parameter logistic function and the IC₅₀ values were 120 nmol l^-1 (N=5) and 810 nmol l^-1 (N=5) for benzamil and amiloride, respectively. (C) Magnitudes of amiloride-sensitive (10 µmol l^-1) I_sc in tissues from hens where shell formation was complete (N=6) compared to tissues where the egg had not entered the shell gland (N=5). ^*Significantly different from control value (P<0.05).