Differential effects of halothane and thiopental on surfactant protein C messenger RNA in vivo and in vitro in rats

Background: Pulmonary surfactant is a complex mixture of proteins and phosp holipids synthetized by alveolar type II cells. Volatile anesthetics have b een shown to reduce surfactant phospholipid biosynthesis by rat alveolar ty pe II cells, Surfactant-associated protein C (SP-C) is critical for the alv eolar surfactant functions. Our goal was to evaluate the effects of halotha ne and thiopental on SP-C messenger RNA (mRNA) expression in vitro in rat a lveolar type II cells and in vivo in mechanically ventilated rats. Methods: In vitro, freshly isolated alveolar type II cells were exposed to halothane during 4 h (1, 2, 4%) and 8 h (1%), and to thiopental during 4 h (10, 100 mu M) and 8 h (100 mu M). In vivo, rats were anesthetized with int raperitoneal thiopental or inhaled 1% halothane and mechanically ventilated for 4 or 8 h, SFC mRNA expression was evaluated by ribonuclease protection assay. Results: In vitro, 4-h exposure of alveolar type II cells to thiopental 10 and 100 mu M increased their SFC mRNA content to 145 and 197%, respectively , of the control values. In alveolar type II cells exposed for 4 h to halot hane 1, 2, and 4%, the SFC mRNA content increased dose-dependently to 160, 235, and 275%, respectively, of the control values. In vivo, in mechanicall y ventilated rats, 4 h of halothane anesthesia decreased the lung SP-C mRNA content to 53% of the value obtained in control (nonanesthetized, nonventi lated) animals; thiopental anesthesia increased to 150% the lung SP-C mRNA content. Conclusions: These findings indicate that halothane and thiopental used at clinically relevant concentrations modulate the pulmonary SP-C mRNA content in rats. In vivo, the additive role of mechanical ventilation is suggested .