Formalin produces depolarizations in human airway smooth muscle in vitro.
Respiratory irritants may result in airway smooth muscle (ASM) depolarization and bronchoconstriction. We examined the effect of formalin on membrane potentials in human ASM in two types of in vitro preparations: strip preparations, which contain functional sensory and motor nerve endings and cultured cells, which lack these nerve endings due to the tissue dissociation process. Depolarizations occurred in atropine-treated strip preparations in response to formalin exposures, but not in similarly-treated cultured cells, suggesting a role for non-cholinergic mediators in formalin-induced depolarization. It is suggested that formalin may act as an irritant to produce bronchoconstriction that is mediated by the release of endogenous substance P (SP) from peripheral sensory nerve endings. This is supported by our observation that exogenous SP produced depolarizations of a magnitude similar to those produced by formalin in both strip preparations and cultured cells. In addition, capsaicin, which releases endogenous SP from nerve endings, produced depolarizations of a magnitude similar to formalin in strip preparations, but was without effect in cultured cells.
Richards
Ira S
IS
Department of Environmental and Occupational Health, College of Public Health, University of South Florida, Tampa, FL, USA. irichard@hsc.usf.edu
DeHate
Robin B
RB
D001285:Atropine / Q000633:toxicity; D016535:Bronchial Hyperreactivity / Q000139:chemically induced*; D016084:Bronchoconstriction; D002211:Capsaicin / Q000494:pharmacology; D004594:Electrophysiology; D005557:Formaldehyde / Q000633:toxicity*; D006801:Humans; D066298:In Vitro Techniques; D007509:Irritants / Q000633:toxicity*; D008564:Membrane Potentials / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000294:innervation; D009467:Neuromuscular Depolarizing Agents / Q000633:toxicity*; D013373:Substance P / Q000378:metabolism; D014132:Trachea / Q000187:drug effects
D007509:Irritants; D009467:Neuromuscular Depolarizing Agents; D005557:Formaldehyde; D013373:Substance P; D001285:Atropine; D002211:Capsaicin