What increases type III procollagen mRNA levels in lung tissue: stress induced by changes in force or amplitude?

We hypothesized that stress determined by force could induce higher type III procollagen (PCIII) mRNA expression than the stress determined by amplitude. To that end, rat lung tissue strips were oscillated for 1 h under different amplitudes [1, 5 and 10% of resting length (L-B), at 0.5 x 10(-2) N] and forces (0.25 x 10(-2), 0.5 x 10(-2) and 10(-2) N, at 5% L-B). Resistance (R), elastance (E) and hysteresivity (eta) were analysed during sinusoidal oscillations at 1 Hz. After 1 h of oscillation, PCIII mRNA expression was determined by Northern-blot and semiquantitative RT-PCR. Control value of PCIII mRNA was obtained from unstressed strips. E and R increased with augmenting force and decreased with increasing amplitude, while eta remained unaltered. PCIII mRNA expression increased significantly after 1 h of oscillation at 10-2 N and 5% L-B and remained unchanged for 6 h. In conclusion, the stress induced by force but not by amplitude led to the increment in PCIII mRNA expression. (C) 2004 Elsevier B.V. All rights reserved.