A quantitative RT-PCR assay of surfactant-associated protein A1 and A2 mRNA transcripts as a diagnostic tool for acute asphyxial death.

Although an immunohistochemical investigation of pulmonary surfactant-associated protein A (SP-A) suggested a characteristic increase in fatal asphyxiation, no particular change was observed in the total amount of SP-A mRNA. SP-A is encoded by two highly similar genes, SP-A1 and SP-A2, which are differentially regulated in the expression. In the present study, to investigate the molecular pathology of SP-A, we established a method for quantitative RT-PCR assay of SP-A1 and SP-A2 mRNA transcripts. Using this method, fatalities from acute mechanical asphyxia (n=12) and drowning (n=9) were examined in comparison with control groups (n=17) of acute myocardial infarction (n=11) and peracute death due to brain lacerations (n=6). The SP-A1/A2 ratio (mean value) was markedly elevated in mechanical asphyxia (6.72) and drowning (5.64), whereas it was low in controls (acute myocardial infarction, 2.80; brain lacerations, 2.56). The analysis of the SP-A1/A2 ratio may assist interpretation of the molecular alterations of SP-A related to acute asphyxial death.