Effect of Desmodium adscendens fraction F1 (DAF1) on tone and agonist‐induced contractions of guinea pig airway smooth muscle

Abstract

AbstractCumulative concentration‐response curves (CCRC) of histamine, carbachol and leukotriene D, (LTD4), and relaxation curves were used to evaluate the nature of the modulation of allergic airway smooth muscle contraction of Desmodium adrcendens fraction F1 (DAF1). DAM significantly increased the maximal contractions (Emax) of tracheal spirals for all three agonists, and significantly increased the pD, values for histamine and carbachol, but decreased that for LTD4. On lung parenchymal strips DAM had no significant effect on the shape of the CCRC, the pD, value or Emax for histamine and carbachol. A significant decrease in the pD, value for LTD4, was observed at DAM concentrations of 0.3 and 0.9mg/mL. At the higher concentration, the decrease was accompanied by an equally significant decrease in the Emax. DAF1 per se, caused relaxation of tracheal spirals. The results indicate that DAF1's effect includes a reduction in sensitivity and responsiveness to LTD4‐induced contractions.