Increased hyaluronan (hyaluronic acid) levels in bronchoalveolar lavage fluid after histamine inhalation.

Hyaluronan (hyaluronic acid) appears in low concentrations in bronchoalveolar lavage fluid from healthy individuals, while increased amounts have been reported in lavage fluid from patients with interstitial lung diseases and allergic asthma. We have earlier reported a strong correlation between the appearance of lavage fluid mast cells and hyaluronan in patients with sarcoidosis and extrinsic allergic alveolitis. The central role of the mast cell in allergic asthma is well documented. In this study we have investigated if challenge with inhaled histamine, a major mast cell component, could influence the appearance of hyaluronan in bronchoalveolar lavage fluid. A more than twofold increase of hyaluronan was seen 24 h after challenge with histamine. This increase correlated with a less pronounced increase of albumin in lavage fluid. Histamine challenge also induced an increase of mast cells, lymphocytes, and granulocytes in the lavage fluid. The observed histamine effect on the hyaluronan recovery during lavage might be explained by a histamine-mediated leakage of interstitial fluid, rich in hyaluronan, to the alveolar space. Mast cell degranulation of histamine may partly underlie the appearance of increased amounts of hyaluronan in lavage fluid from patients with interstitial lung diseases and allergic asthma.