[Effects of isoflurane on lung surfactant protein A in rats]

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.

Thirty-two male Wistar rats were randomly divided into 4 groups: control group received 40% (volume fraction) O2 inhalation (40% O2, n=8); 0.7% isoflurane group (n=8), 1.5% isoflurane group (n=8), and 2.0% isoflurane group (n=8). They were treated with 40% O2 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.

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 (P<0.01); 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 (P<0.01).

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.