Mechanical properties of pulmonary arteries from sensitized dogs

On the basis of isometric dose-response studies, we (J. Pharmacol. Exp. Ther. 219:551-557, 1981) have reported that the ovalbumin-sensitized (S) canine pulmonary artery (PA) is hypersensitive and hyperractive to histamine compared with that from a littermate control (C) in vitro. In this study, our aim was to determine whether the maximal velocity of shortening (Vmax) measured in strips of electrically stimulated SPA and CPA differed. Vmax (velocity at zero load) was obtained by analysis of force-velocity curves from these tissues using the equation (P + a) (V + b) = (Po + a)b, in which P is load, Po is maximum tetanic tension, V is shortening velocity, and a and b are asymptotic values in units of force and velocity. The Vmax values derived for SPA and CPA are 0.188 +/- 0.029 (SE) and 0.113 + 0.017 lo/s, respectively, lo being defined as that length at which Po is obtained. This result indicated that the Vmax value of SPA is significantly (P less than 0.05) different from that of CPA. The b values for SPA [0.034 +/- 0.003 lo/s] and for CPA [0.025 +/- 0.004 lo/s] were also significantly different. However, the force constants a and Po were unchanged in the SPA and CPA. SPA also had a greater isotonic shortening capacity than CPA. These findings indicate that mechanical properties of SPA are altered and lend an understanding of the hyperreactivity of these vessels in the sensitized model.