Exercise-induced release of histamine and neutrophil chemotactic factor in atopic asthmatics

Sodium cromoglycate and atropine block the fall in FEV1 but not the cough induced by hypotonic mist

In a group of patients with mild asthma the inhalation of mist derived from ultrasonically nebulised distilled water caused an increase in cough and a fall in FEV1. Double blind administration for five minutes of sodium cromoglycate (from an original solution containing 30 mg/ml) or atropine (2 mg/ml) by inhalation from a Minineb nebuliser, 30 minutes before the mist challenge, caused a significant reduction in the fall in FEV1 (p less than 0.05), but not in cough, by comparison with the protection afforded by placebo (saline). In a second study the fall in FEV1 caused by the inhalation of distilled water was not significantly different from that seen in response to hypotonic sodium chloride (1.7 g/l, 58 mmol/l), but both produced a significantly greater fall than did a similar mist containing sodium cromoglycate at an original concentration of 10 mg/ml (58 mmol/l). The results show that both atropine and sodium cromoglycate can block the fall in FEV1 due to mist and that protection by sodium cromoglycate is immediate. These results suggest that sodium cromoglycate blocks the nervous reflexes concerned in the response to mist, probably in the afferent limb of the reflex.

Plasma histamine and catecholamines during carbachol-induced bronchoconstriction in normal subjects

To determine (1) whether changes in plasma histamine occurred during provoked bronchospasm and (2) if so, whether such changes could be related to variations in plasma catecholamines, venous plasma histamine and catecholamines were measured during a dose-response carbachol challenge in eight healthy volunteers. A significant rise in plasma histamine was observed, whereas induced bronchoconstriction was small, 80% +/- 4% of initial specific airway conductance. There was no further increase in plasma histamine, whereas induced bronchoconstriction became more marked (70%, 60%, and 50% of specific airway conductance initial value). Plasma catecholamines did not change throughout the study. We conclude that mast cell degranulation occurs during a carbachol challenge, and that the variations in plasma histamine are not related to changes in plasma catecholamines.

Allergies, mediators and asthma

Asthma is a term that has been used for centuries to describe states of breathlessness associated with wheezing. However, there are well-known difficulties in defining asthma, as it encompasses such a broad clinical spectrum ranging from mild, rapidly reversible, bronchospasm to severe, intractable, chronic airflow obstruction. Moreover, reversibility of airflow obstruction, a cardinal feature used to identify asthma, may be demonstrated only with difficulty in certain cases, such as severe, acute asthma attacks, which necessitate several days of treatment before any reversibility can be achieved.

Measurement of plasma histamine by stable isotope dilution gas chromatography-mass spectrometry: methodology and normal values

A new method for the determination of histamine by stable isotope dilution mass fragmentography is described. The method is specific, sensitive, and accurate, resulting in a within-day coefficient of variation of 4.1% and a day-to-day variation of 7.9%. It was shown that the first blood sample after a venipuncture can contain an artificially elevated plasma histamine concentration. Platelets contain about 7 pmol histamine/10(9) cells. Serum histamine was elevated about four times in comparison with plasma histamine. This phenomenon was mainly ascribed to degranulation of basophilic leukocytes by complement activation during blood clotting. Normal values for plasma histamine were (n = 25) 2.07 +/- 0.75 nmol/liter (mean +/- 1 SD), which is one of the lowest values reported up to now.

[Blockade of exercise-induced bronchial asthma by fenoterol]

The bronchoconstrictor response to cold air breathing during exercise shows a wide interindividual variation in asthmatic patients. We investigated whether the protective effect of a single, inhaled dose of 0.2 mg fenoterol powder is dependent on the severity of airways obstruction, following placebo pretreatment of an inhalative thermal burden precisely matched in terms of respiratory heat exchange. In ten asthmatic patients 0.2 mg fenoterol powder or placebo were administered via an inhalator in a single blind and random order fashion on separate days. Lung function was measured before and 30 min after treatment (baseline value) and 3, 10, 15 and 30 min after an inhalative provocation consisting of cold air breathing during exercise. After placebo the maximal increase of airway resistance compared to the baseline value ranged from 682% to 50% (means +/- SD: 344.1 +/- 312.2) whereas fenoterol shifted the corresponding data to 58% and -23.0% (means +/- SD: 13.4 +/- 29.2). The protective effect of fenoterol did not depend on the reactivity of the airways to the stimulus applied. The results indicate that the inhalative pretreatment with 0.2 mg fenoterol powder is sufficient to block exercise-induced asthma even in those patients whose airways are highly sensitive to respiratory heat loss.

Exercise-induced late asthmatic reactions with neutrophil chemotactic activity

Two adults and 13 children with exercise-induced asthma had both immediate and late reductions in forced expiratory volume in one second (FEV1) after treadmill exercise. The late reactions developed 4 to 10 hours after exercise and in each instance were associated with wheezing or chest tightness (or both). Increases in neutrophil chemotactic activity, measured in the 2 adults and in 11 of the children, accompanied the reductions in FEV1 in all these subjects. In contrast, four other adults with only an immediate fall in FEV1 after exercise had only an initial elevation in neutrophil chemotactic activity, with no subsequent increase for the remaining 24-hour period. The agent responsible for the neutrophil chemotactic activity released during exercise-induced late reactions appeared to be identical to that released during immediate reactions. These observations suggest that some patients with exercise-induced asthma have late reactions that, as in the case of antigen-induced bronchoconstriction, are accompanied by the release of neutrophil chemotactic activity.

The link between exercise, respiratory heat exchange, and the mast cell in bronchial asthma

There are two apparently conflicting theories on the pathogenesis of exercise-induced asthma. One view is that exercise-induced asthma is directly related to respiratory heat exchange and that mast cells are not involved. The other theory explains exercise-induced asthma on the basis of a temperature-independent release of mast-cell mediators. A theory is put forward here that airway cooling in asthmatic subjects during exercise leads directly to mast-cell degranulation and that this explains the association between exercise, respiratory heat exchange, and mediator release.