Effect of histamine on the length-tension properties of guinea pig trachealis muscle.

The isotonic length-tension properties of excised live guinea pig trachealis muscle have been determined as a function of histamine concentration. Over the range of histamine concentrations studied, a family of curves corresponding to the total and active tensions were obtained. Reciprocal plots of the tension-concentration data revealed a length dependence of the affinity constant of histamine for its receptor The tensions and lengths below resting were considered to be of special importance because of the role of muscle contraction in airway closure. A mechanochemical model for shortening and reelongation of the trachealis muscle during anaphylaxis has been proposed on the basis of this data. By comparing the force-length properties of the muscle at the lowest histamine concentration, it was suggested that the formation of a histamine-Ca++ receptor complex causes an increase in the rigidity of the muscle membrane. The complete range of lengths, tensions, and concentrations must be employed in order to propose a mechanism of action from mechanical data alone.