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* From the Istituto di Fisiologia Umana, Università degli Studi, Milano, Italy, and the Dipartimento di Biochimica "A. Castellani," Università degli Studi, Pavia, Italy.
Correspondence to: G. Miserocchi, MD, Istituto di Fisiologia Umana, Universita di Milano, Via Mangiagalli 32, 20133 Milano, Italy.
In anesthetized rabbits, pulmonary interstitial pressure (Pip) was measured by micropuncture technique performed through a pleural window during the development of lung edema induced either by IV saline solution loading or elastase administration (7 IU). In control condition, Pip at heart level was -10 ± 2 (1 SD) cm H2O. In both edema models, Pip increased to about +5 cm H2O (phase of interstitial edema) and then dropped to about 0 cm H2O in severe edema, indicating a loss of the mechanical integrity of pulmonary tissue matrix.1 2 3 Pip correlated to structural and functional modifications of proteoglycans (PGs), the major interfibrillar components of extracellular matrix (ECM). In severe edema, PG ability to bind other ECM components was markedly reduced, and electrophoretic and gel-filtration analyses showed a PG breakdown, mainly affecting the protein moiety. Qualitative zymography performed on lung extracts showed two main gelatinolytic bands at about 92 kd and 72 kd, identified by specific antisera as progelatinase B and progelatinase A, respectively and, in addition, two minor bands corresponding to their proteolytically activated forms. The intensity of all bands and the relative proportions of the proteolytically activated forms increased markedly with edema development. The results suggest that the development of hydraulic- and elastase-induced pulmonary edema is associated with an increase of endogenous protease activities, which eventually leads to a loss of the native architecture of ECM.
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