Figure 4. Effect of propofol and etomidate on KCl-induced responses in the rat trachea. (A) Effect of KCl (110 mM) on [Ca²+]ⁱin freshly isolated smooth muscle cells loaded with indo-1. Each trace is representative of 7–24 different cells. (B) Percentage of responding cells (as a percentage; left ordinate scale) and amplitude of the first [Ca²+]ⁱpeak (the maximal increase above resting baseline concentration)(expressed as nanomoles; right ordinate scale) in control cells (open columns), in the presence of propofol (3 x 10 sup -4 M; solid columns) and in the presence of etomidate (10 sup -4 M; cross-hatched columns). Vertical bars are SEM. *P < 0.05. (C) Mean concentration-response curve for KCl in the absence of anesthetic compounds (closed circles) and in the presence of propofol (3 x 10 sup -4 M; open triangles down) and of etomidate (10 sup -4 M; open triangles up) in rat isolated tracheal rings. Each symbol represents a mean value calculated from five different specimens. Contractile force is expressed as a percentage of a reference response to acetylcholine (1 mM). Vertical bars indicate SEM. *P < 0.05.