Potentiation by tumour necrosis factor‐α of calcium signals induced by bradykinin and carbachol in human tracheal smooth muscle cells

Abstract

The effect of tumour necrosis factor‐α (TNFα) on the increase in cytosolic free calcium ([Ca2+])i induced by carbachol and bradykinin (BK) was investigated in human tracheal smooth muscle cells in culture (TSMC). BK (10−12–10−9m) and carbachol (10−7–10−3m) produced a concentration‐dependent increase in [Ca2+]i (pD2 = 10.73 ± 0.05 and 5.57 ± 0.03 respectively). The increase in [Ca2+]i was significantly enhanced for both agonists in TNFα‐treated cells (10 ng ml−1 for 24 h). However, pD2 values were not modified (10.78 ± 0.03 and 5.62 ± 0.04 for BK and carbachol, respectively) suggesting that no change in the apparent receptor affinity occured. Thus, TNFα induced‐alterations in Ca2+ homeostasis in human TSMC may be a key mechanism underlying airway hyperreactivity. 1995 British Pharmacological Society