Distribution of hyaluronate and hyaluronate receptors in the adult lung.

In the present study, we have examined the distribution of both hyaluronate receptors and hyaluronate in adult hamster lung. The receptor for hyaluronate is a transmembrane glycoprotein of Mr 85,000 that interacts with actin filaments and is thought to mediate many of the effects that hyaluronate has on cell behaviour, such as cell-to-cell adhesion and migration. It was localized histochemically with a monoclonal antibody, designated as K-3, which specifically binds to the receptor. Hyaluronate was detected by a biotinylated form of cartilage proteoglycan, which binds with high affinity and specificity to hyaluronate. At the light-microscopic level, both hyaluronate and its receptor were present on the basolateral surfaces of bronchial and bronchiolar epithelium, suggesting that these two components interact with each other. This interaction may be important for maintaining the attachment of the epithelium to the basement membrane. In addition, hyaluronate was present in the adventitial regions of large pulmonary blood vessels. Receptors for hyaluronate were also evident on the surfaces of pulmonary macrophages, as demonstrated by the fact that K-3 immunoreactive cells coincided with cells positive for non-specific esterase, a characteristic feature of macrophages. The receptors on pulmonary macrophages probably mediate the effects that hyaluronate has on these cells with respect to cell-to-cell adhesion and migration.