Late asthmatic reactions and changes in histamine responsiveness provoked by occupational agents.

The temporal and quantitative relationship between increases in airway responsiveness and late asthmatic reactions provoked by inhalation challenge with occupational agents was studied in nine individuals who underwent a total of thirteen active inhalation challenge tests with one of the following agents: toluene diisocyanate (TDI), maleic anhydride (MA), trimellitic anhydride (TMA), carmine, or colophony (pine wood resin). Airway responsiveness to inhaled histamine (histamine PC20) was measured before and at approximately 3 and 24 h after control and active challenge exposure, when, on all but four occasions, FEV1 was within 10% of pre-challenge values. Significant increases (p less than 0.02) in histamine responsiveness were present at 3 h following challenge exposures which subsequently provoked a definite late asthmatic reaction (FEV1 decrease greater than 15% 3-11 h post challenge). These increases in histamine responsiveness were significantly greater than those at 3 h following the challenges which provoked an isolated early (FEV1 decrease less than 6% 3-11 h post-challenge) or equivocal late asthmatic reaction (FEV1 decrease 6-15% 3-11 h post-challenge) (p less than 0.03). Although histamine responsiveness remained high at 24 h after challenges provoking late asthmatic reactions (p less than 0.05), this was less than the increase at 3 h and not significantly different from the PC20 at 24 h after challenges provoking either single early or equivocal late asthmatic reactions.(ABSTRACT TRUNCATED AT 250 WORDS)