Effects of isoflurane on lung surfactant protein A in rats

Objective:To examine the effects of different concentrations of Isoflurane on the level of surfactant protein A(SP-A) and the expression of SP-A mRNA in the lung of rats.Methods: Thirty-two male Wistar rats were randomly divided into 4 groups: control group received 40%(volume fraction) O_2 inhalation(40% O_2,n=8);0.7% isoflurane group(n=8),1.5% isoflurane group(n=8).They and 2.0% isoflurane group(n=8).They were treated with 40%O_2 with 0.7%,1.5% and 2.0% isoflurane respectively.In each group,the rats inhaled experimental gas for 8 hours,and then were put to death immediately.Morphological changes of type Ⅱ pneumocytes were observed by transmission electron microscopy.Surfactant protein content in broncho-alveolar lavage fluid(BALF) was measured with Western Blotting.The level of intracellular SP-A was examined with immunohistochemistry(IHC).To assess the relative levels of SP-A mRNA in lung tissue,reverse transcriptase-polymerase chain reaction(RT-PCR) was used with the co-amplification of the "housekeeping" gene GAPDH as internal control.Results: Morphological changes of type Ⅱ pneumocytes were distinct in 1.5% isoflurane and 2.0% isoflurane groups.Isoflurane,after three doses,significantly reduced the SP-A content in BALF.Control group,(437 112)±25 654;0.7%Isoflurane group,355 789±28 116;1.5%Isoflurane group,238 554±31 531;(2.0%) Isoflurane group,223 632±25 710(P0.01); Intracellular SP-A content of 1.5% and 2.0% isoflurane groups was less than that of the control,whereas 0.7% isoflurane groups did not show any significant difference from the control.RT-PCR indicated a reduced expression of SP-A mRNA in the lung after 1.5% and 2.0% isoflurane exposure.Control group,1.47±0.18;1.5%Isoflurane group,1.19±(0.13;)2.0%Isoflurane group,1.13±0.12(P0.01).Conclusion:These findings indicate that 1.5% or more than 1.5% Isoflurane exposure for eight hours could decrease the expression of the SP-A mRNA and synthesis of SP-A in rats,and maybe it could also affect the secretion and reuse.