Ozone effects on alpha-1-proteinase inhibitor in vivo: blood plasma inhibitory activity is unchanged

The possible oxidative inactivation of human blood plasma alpha-1-proteinase inhibitor (alpha-1-PI) by inhaled ozone was assessed. Eleven male volunteers (non-smokers) were exposed to 0.5 ppm ozone for four hours on two consecutive days and ten control subjects were exposed to air under the same conditions. Blood plasma samples, drawn before and after treatment, were assayed for total alpha-1-PI, total protein and elastase inhibitory activity. The amount of active alpha-1-PI in plasma samples was quantitated by titrating porcine pancreatic elastase with increasing amounts of plasma. The importance of constructing titration curves for determinations of this type was demonstrated. No differences were noted in the ratios of total alpha-1-PI/total protein or elastase inhibitory activity/total alpha-1-PI in the plasma from ozone exposed individuals relative to controls. Although inhaled ozone did not result in any significant decrease in the activity of blood plasma alpha-1-PI, these findings do not preclude the possibility of oxidative inactivation of a alpha-1-PI in the lung.