Role of histamine in allergen-induced asthmatic reactions, bronchial hyperreactivity and inflammation in unrestrained guinea pigs

In a new model using conscious, unrestrained and ovalbumin-sensitized guinea pigs, we investigated the effects of the selective histamine H1 receptor antagonist, mepyramine, on the development of allergen-induced early and late asthmatic reactions, bronchial hyperreactivity and airway inflammation, having each animal as its own control. In guinea pigs responding to a first allergen exposure with an early as well as a late asthmatic reaction (82% of the animals) a second, identical, allergen provocation was performed, in the absence (control) or presence of 1 mg/ml mepyramine aerosol, inhaled for 10 min, 1 h before provocation. The mepyramine treatment significantly reduced both early and late asthmatic reactions and prevented the development of bronchial hyperreactivity to histamine and methacholine after both reactions. Examination of the bronchoalveolar lavage fluid 24 h after the second allergen provocation revealed a general reduction of inflammatory cells after mepyramine treatment. The results indicate that histamine, released during the early asthmatic reaction, contributes to the development of the late asthmatic reaction as well as of early and late bronchial hyperreactivity, possibly via an effect on airway inflammation.

The relationship between mast cell-mediator release and bronchial reactivity in allergic asthma

The relationship between mast cell-mediator release and nonspecific bronchial reactivity was investigated in allergen-induced asthma. Two groups of subjects with asthma, one group with markedly reactive airways (provocative concentration of methacholine causing a 20% fall in FEV1, 0.07 mg/ml) and the other group with less reactive airways (provocative concentration of methacholine causing a 20% fall in FEV1, 3.83 mg/ml), had allergen bronchoprovocation. After challenge, bronchoconstriction was measured as change in specific airway conductance (SGaw), and mast cell-mediator release was measured as change in both plasma histamine and serum neutrophil chemotactic activity (NCA). In the group with more reactive airways, allergen challenge, while it produced a mean fall in SGaw of 58.1%, was not associated with any significant increase in plasma histamine from a mean resting level of 3.69 nmol/L-1. In contrast, a comparable mean fall in SGaw of 52.4% in the group with less reactive airways was associated with a significant (p less than 0.005) increase in plasma histamine from 1.17 to 3.60 nmol/L-1, maximal 5 minutes after allergen challenge. There were, however, significant increments in serum NCA in both groups with asthma after allergen challenge. The changes in NCA in the group with less reactive airways (136.7 +/- 38.1% above baseline; p less than 0.01; 1% sera dilution) were significantly greater (p less than 0.05) than changes identified in the group with more reactive airways (68.3% above baseline; p less than 0.01; 20% sera dilution). These findings directly support the concept that both mast cell-mediator release and nonspecific bronchial reactivity are separate factors that influence the airway response to inhaled allergen in asthma.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma histamine after methacholine, allergen, and aspirin challenges

Plasma histamine levels were measured by radio-enzymatic technique in seven patients following 10 challenges: five methacholine challenge tests, four antigen inhalation challenge tests, and one oral aspirin challenge test. Baseline plasma histamine was the same in all patients except in the aspirin-challenged patient, who had a higher baseline histamine level. There was no statistical change in the level of histamine throughout the test in either the methacholine-challenged or the antigen-challenged patients, whereas there was a marked increase in histamine levels in the aspirin challenged patient. A possible explanation is that methacholine and antigen are inhaled and therefore have primarily local effects on the lung, whereas oral aspirin has a systemic effect with consequently systemic changes in histamine which are detectable as changes in plasma level.

Bronchial hyperreactivity after treatment with sodium cromoglycate in atopic asthmatic patients not exposed to relevant allergens

The bronchial hyperreactivity, measured as the responsiveness to histamine, was studied in 14 atopic patients before, during, and after 4 wk of treatment with sodium cromoglycate (SCG) and placebo in a double-blind, randomized, crossover study. The patients were not exposed to relevant allergens during the study. The variations in provocation concentrations corresponding to 20% decrease in FEV1 (PC20) were small during both placebo and active drug treatment. After SCG treatment, PC20 increased (less responsiveness) in nine of the 14 patients, especially in those with low PC20 values. The difference between placebo and active drug treatment was not statistically significant. Although SCG has a mediator-inhibiting effect, this study gave no support for the assumption that inhibition of mediator release leads to a reduction of the bronchial hyperreactivity in atopic asthmatic subjects who are not exposed to relevant allergens.

Urinary N tau-methylhistamine during early and late allergen-induced bronchial-obstructive reactions

Urinary N tau-methylhistamine, a unique histamine metabolite, was determined in 29 patients with bronchial asthma before and after inhalation of a control solution on 1 day and before and after allergen inhalation on another day. Twenty-eight patients had an early bronchial-obstructive reaction, defined by a decrease in FEV1 of 20% or more within 1 hr after allergen inhalation. A late bronchial-obstructive reaction, 3 to 8 hr after allergen inhalation, was found in 16 patients. The early bronchial-obstructive reaction was attended with a significantly increased N tau-methylhistamine excretion. The fall in FEV1 was correlated with the degree of bronchial hyperreactivity to histamine, but no significant correlation was found with the increase in urinary N tau-methylhistamine excretion. During the late reaction there was no significant difference in the change in N tau-methylhistamine excretion when the change was compared with that of the control day. These results suggest that a renewed degranulation of lung mast cells during the late bronchial-obstructive reaction is unlikely.