The expression of a novel stress protein ‘150-kDa oxygen regulated protein’ in sudden infant death

The oxygen regulated protein 150-kDa (ORP-150) is only induced in hypoxic conditions. We performed an immunohistochemical and morphometrical study on the expression of ORP-150 in the brains of sudden infant death (SID) victims. The cerebral cortexes of 18 infants were used for this study. Each tissue section was incubated with anti-ORP-150 polyclonal antibodies and the number of ORP-150 positive cells was counted. In the cluster analysis, the 18 cases were classified into three groups (A–C groups). Group A was composed of six sudden infant death syndrome (SIDS) cases and its mean value of ORP-150 positive cells was 66.75±3.44, Group B (six severe respiratory infectious disease such as pneumonia and bronchitis including sepsis): 39.50±2.52 and Group C (five SIDS and one severe respiratory infectious disease): 16.00±2.92, respectively. These results might reflect chronic hypoxic condition before death, because ORP-150 is only induced when a hypoxic condition exist, but not acute hypoxia. And chronic hypoxic state is likely to be antecedent to SIDS. Therefore, immunohistochemical analysis of OPR-150 in the brain of SID cases may be very useful to differentiate between SIDS and acute asphyxia.