Effect of elastase pretreatment on rat lung strip induced constriction

On exposure to contractile agonists, peripheral smooth muscle shortens and induces distortion in lung parenchyma. To assess the influence of elastic integrity on lung tissue constriction, 24 rat lung strips were oscillated in organ bath, at a fixed frequency of 1 Hz, and exposed to acetylcholine (Ach) 10(-1) M, before and after incubation with pancreatic porcine elastase (PPE). Before the post-PPE Ach challenge, 11 samples were re-stretched to recover control elastance value. Tissue elastance (Etis), resistance (Rtis), and minimum stress (sigma(min)) were calculated cycle-by-cycle. PPE exposure significantly decreased Etis by 8.50+/-1.91%, and sigma(min) by 33.2+/-3.6%. PPE digestion affected the dynamic of mechanical changes during constriction in non re-stretched samples, but not in re-stretched ones. We conclude that lung tissue damage induced by PPE impairs the transmission of forces generated by lung tissue constriction, challenging mechanical interdependence. The intrinsic properties of contractile machinery seem unaffected by PPE digestion.