[Relaxant effects of oligopeptides isolated from the tracheal mucosa and pulmonary parenchyma on the smooth muscle of isolated rat trachea].

Relaxant effect of oligopeptides extracted from tracheal mucosa (PTM), lung parenchyma (PLP), aortal wall (PAW) and thymic gland (PTG) was investigated using acetylcholine-induced constriction of tracheal strips. Time of 50 percent relaxation of constricted strips treated with saline, atropine or peptides was measured. Both PTM and PLP in concentrations 10(-6)-10(-3) g/ml accelerated relaxation in dose-dependent manner, however this effect was less prominent compared with atropine. Relaxant effect of PTM was found using different parts of trachea (cervical of thoracal), indicating independence of PTM action of intramural ganglia which are present only in the thoracal part. PAW and PTG did not show any significant effect on relaxation time. These results suggest the presence of oligopeptides, capable to relax airways smooth muscle, in tracheal mucosa and lung parenchyma.