DIFFERENTIAL DISTRIBUTION OF ELASTIC SYSTEM FIBERS IN CONTROL AND BRONCHOCONSTRICTED INTRAPARENCHYMATOUS AIRWAYS IN THE GUINEA-PIG LUNG

The elastic system fibers were studied at the light microscopic level by using Weigert's resorcin-fuchsin method after oxidation. This study was designed to describe the distribution of these fibers in intrapul monary guinea-pig airways and to characterize their conformational cha nges during bronchoconstriction induced by methacholine aerosol. Airwa ys present a palisade of elastic system fibers lust beneath the epithe lial basement membrane; these fibers are also present in the adventiti al connective tissue. Thin fibers link the fibers located in the palis ade among themselves and also connect them to those fibers located in the bronchial adventitial tissue, by traversing the airway smooth musc le. During bronchoconstriction, the fibers located beneath the epithel ial basement membrane are divided into two components: one follows the epithelial invaginations towards airway lumen, while the other popula tion remains attached through airway smooth muscle to the fibers locat ed in the adventitial connective tissue. At the ultrastructural level, the findings corroborated those of the light microscopy and in additi on, disclosed that typical mature elastic fibers and also elaunin fibe rs attach directly to the basal lamina, a feature that has not been re ported previously in other tissues studied. This configuration is comp atible with the idea that fibers of the elastic system restrict the mu cosal folding during bronchoconstriction, and may also provide energy to restore airway configuration to its normal status after contraction .