Lack of effect of leukotriene D<sub>4</sub> on Ca‐uptake in airway smooth muscle

The effects of verapamil on leukotriene D4 (LTD4)‐ and KCl‐induced contractions and 45Ca‐uptake were examined in guinea‐pig isolated tracheal smooth muscle. Both LTD4 (0.1 to 200 nmol l−1) and KCl (8 to 125 mmol l−1) produced concentration‐dependent increases in tension in the tracheal preparations. Verapamil (1 μmol l−1) inhibited the tension responses induced by both LTD4 and KCl. LTD4 failed to increase the lanthanum‐resistant Ca content of tracheal smooth muscle at either low (EC25; 3 nmol l−1) or high (EC90; 50 nmol l−1) concentrations. Verapamil did not modify this result. KCl (90 mmol l−1) increased the lanthanum‐resistant Ca content of the smooth muscle by approximately 60% over basal levels. This effect was completely inhibited by verapamil (1 μmol l1). It is concluded that in this tissue, LTD4 utilizes principally an intracellular source of Ca2+ to initiate contraction whereas KCl is dependent upon the uptake of Ca2+ from the extracellular compartment. It is suggested that the inhibitory effects of verapamil may reflect an intracellular mechanism of action directed against Ca2+ release initiated by LTD4.

Lack of effect of leukotriene D₄ on Ca‐uptake in airway smooth muscle Journal Articles