Effect of Smoking on Functional Activity of Plasma a1-Protease lnhibitor*

We determined the levels of a,-protease inhibitor, the plasma trypsin-inhibiting capacity (TIC), and elastase-inhibiting capacity (EIC) in 29 nonsmokers and 30 smokers, who were healthy volunteers matched for age (mean age, 39 ± 12 years [± SD]). The functional activity of plasma a1protease inhibitor (in micrograms of enzyme inhibited per microgram of a,-protease inhibitor) was slightly but significandy lower in smokers, compared with nonsmokers, both for TIC and EIC (smokers’ TIC and EIC were 88.0 ± 16.2 percent (± SD) and 90.4 ± 17.9 percent of the respective mean values in nonsmokers; p<O.O5). Among smokers, there was a significant negative correlation (r 0.37;