Effect of phenylephrine on alveolar fluid clearance in ventilator-induced lung injury.

Objective: To investigate the effect of phenylephrine (an α-adrenergic agonist) on alveolar fluid clearance (AFC) in ventilator-induced lung injury and the possible mechanism involved.
Methods: A total of 170 male Wistar rats were randomly allocated into 17 groups (n=10) using random number tables. Short-term (40 minutes) mechanical ventilation with high tidal volume (HVT) was performed to induce lung injury, impair active Na+ transport and lung liquid clearance in the rats. Unventilated rats served as controls. To demonstrate the effect of phenylephrine on AFC, phenylephrine at different concentrations (1×10(-5), 1×10(-6), 1×10(-7), 1×10(-8), and 1×10(-9) mol/L) was injected into the alveolar space of the HVT ventilated rats. To identify the influence of adrenergic antagonists, Na(+) channel, and microtubular system on the effect of phenylephrine, phenylephrine at 1×10(-5) mol/L combined with prazosin (an α1-adrenergic antagonist, 1×10(-4) mol/L), yohimbine (an α2-adrenergic antagonist, 1×10(-4) mol/L), atenolol (a β1- adrenergic antagonist, 1×10(-5) mol/L), ICI-118551 (an β2-adrenergic antagonist, 1×10(-5) mol/L), amiloride (a Na+ channel blocker, 5×10(-4) mol/L), ouabain (a Na(+)/K(+)-ATPase blocker, 5×10(-4) mol/L), colchicine (a microtubular disrupting agent, 0.25 mg/100 g body weight), or β-lumicolchicine (an isomer of colchicine, 0.25 mg/100 g body weight) were perfused into the alveolar space of the rats ventilated with HVT for 40 minutes. AFC and total lung water content were measured.
Results: Basal AFC in control rats was (17.47±2.56)%/hour, which decreased to (9.64± 1.32)%/hour in HVT ventilated rats (P=0.003). The perfusion of phenylephrine at 1×10(-8), 1×10(-7), 1×10(-6), and 1×10(-5) mol/L significantly increased the AFC in HVT ventilated rats (all P<0.05). This effect of phenylephrine on AFC was suppressed by prazosin, atenolol, and ICI-118551 in HVT ventilated rats by 53%, 31%, and 37%, respectively (all P<0.05). The AFC-stimulating effect of phenylephrine was lowered by 33% and 42% with amiloride and ouabain, respectively (both P<0.05). Colchicine significantly inhibited the effect of phenylephrine (P=0.031).
Conclusion: Phenylephrine could increase the AFC in HVT-ventilated rats and accelerate the absorption of pulmonary edema.