生体負担度評価指標としての唾液中分泌型IgAの基礎的検討

Abstract

Recently, there have been several studies investigating biomarkers of occupational stress. Salivary secretory immunoglobulin A (sIgA) is the dominant immunoglobulin in secretory fluids such as saliva, nasal and gastrointestinal juice, and it is considered to play a part in the first immunological protection on mucosal surfaces. SIgA concentration has also been reported to be affected by various forms of physical stress, and to be a non-invasive marker of occupational stress. These investigations, however, did not consider the diurnal cycle and daily variation of sIgA concentration. Moreover, changes in sIgA concentration after a bout of exercise have not yet been demonstrated. In this study, the potential of sIgA as a workload indicator was evaluated using two experiments. The first investigated diurnal cycle and daily variation of sIgA concentration. The second measured sIgA concentration after a bout of exercise on a treadmill. For study 1, sIgA concentration at 0900 was significantly higher than those at other times investigated. No significant differences were observed among sIgA concentrations from 1,100 to 1,700. There was no daily variation in sIgA concentrations among the 5 days tested. For study 2, sIgA concentration decreased in response to treadmill exercise when the levels of overload were above 65 percent Maximum Heart Rate (percent MaxHR). This decrease appeared only 5 minutes after achieving a definit percent MaxHR, and the minimum level was recorded at the end of the treadmill exercise session. There was a negative correlation between the ratio of post/pre treadmill sIgA concentrations and the level of overload above 65 percent MaxHR during the treadmill session. The present results demonstrated that a bout of exercise decreases sIgA concentration in association with the level of overload above 65 percent MaxHR. SIgA concentration provide a particularly useful indicator of workload.