The surfactant protein A(SP-A) is important in the regulation of surfactant secretion, synthesis and recycling. Since the acute respiratory distress syndrome(ARDS) is usually viewed as the functional and morphological expression of a similar underlying lung injury caused by a variety of insults and since abnormalities in surfactant function have been described in ARDS, the authors investigated the different effects of endotoxin and thiourea on the accumulation of mRNA encoding SP-A.

Sprague-Dawley rats were given 5 mg/kg intraperitoneal endotoxin from Salmonella enteritidis and 3.5 mg/kg intraperitoneal thiourea and sacrified at different time periods.

1) SP-A mRNA was significantly increased 67.0% in 6 hours and 73.4% in 24 hours after 5 mg/kg endotoxin treatment respectively(P<0.005, P<0.005). 2)SP-A mRNA was significantly decreased 32.9% in 24 hours after 3.5 mg/kg thiourea treatment(P<0.05).

These results indicate that the differential regulation of surfactant protein A in vivo is evident and suggest that surfactant protein A might be differentially regulated during different kind of insults of lung injury at different time periods without altering lung wet to dry ratios.