Figure 1.

Average single exposure concentration‐contraction curves to endothelin‐1 in rat (A) mesenteric artery (n = 15) and (B) pulmonary artery (n = 15), pretreated with L‐NAME 100 μmol L⁻¹, in the absence Control, (0 μmol L⁻¹) or presence of bosentan 1, 10 or 100 μmol L⁻¹. Data are expressed as % KPSS maximum contraction (y axis). (C) Clark plot display for the relationship in the rat mesenteric artery between the endothelin‐1 pEC ₅₀ values (y axis; −log M) and −log(B + K_B) where B is concentration of bosentan (0, 1, or 10 μmol L⁻¹) and K_B is the global‐fitted dissociation constant. The error bars are ± 2 SEM of the difference between the nonlinear regression‐fitted pEC ₅₀ values for endothelin‐1 and the pEC ₅₀ values fitted for the individual artery for each concentration of bosentan (B). (D) The pEC ₅₀ values for the endothelin‐1 curves in (A) and (B) are plotted on the y axis against the bosentan concentration (x axis) for each artery type. Vertical error bars in (A, B, and D) are ± 1 SEM (those not shown are contained within the symbol). Horizontal error bars (A‐B) represent the EC ₅₀ ± 1 SEM. n, number of arteries isolated from separate animals. *P < .05, pEC ₅₀ values compared with respective control (0 μmol L⁻¹) pEC ₅₀ values. Variations in n are due to violation of predetermined criteria: mesenteric arteries that contracted to KPSS with <3 mN force or pulmonary arteries that contracted to KPSS with <1 mN force