Inhibition of PMA-induced human neutrophil superoxide anion (O2•−) production by three different nebulized formulations of tPA as measured by the rate of cytochrome c reduction (mM min−1). production Formulations #1 (A), #25 (B), and #27 (C) reduced O2•− by 84, 50, and 58%, respectively. Data represent the mean (±SEM) of results from at least seven separate experiments.