FIGURE 8.
Effect of bile acid alone versus combined effect of chymotrypsin and bile acid on wild-type or mutant δβγENaC. A, linear regression analysis of the relative stimulatory effects of CDCA versus chymotrypsin in the presence of CDCA in δβγ- (○) and δβN521CγENaC- (□) expressing oocytes. Each point represents a single measurement (relative increase of Iami by chymotrypsin + CDCA versus relative increase of Iami by CDCA) from similar experiments as shown in 7, A and B. ●, ■ = mean values with S.E. for δβγ and δβN521CγENaC, respectively. Calculated linear regressions with proportionality coefficients (k) are depicted by dashed lines. B, linear regression coefficients (k) calculated similarly as in A for experiments using the indicated bile acids (CA, t-CA, DCA, t-DCA, CDCA, or t-CDCA) in oocytes expressing wild-type (δβγ) or different δβγENaC mutants: δβN521Cγ, δβN521Aγ, δβN521Sγ, δβS520Cγ, δA527Nβγ, and δβγN530A (k ± S.E.; N = 2–3; 10 ≤ n ≤ 38; ***, p < 0.001 when compared with wild-type δβγENaC (δβγ), n.s., not significantly different when compared with wild-type δβγENaC (δβγ); one-way ANOVA with Bonferroni post hoc test).