Airway epithelial cells regulate membrane potential, neurotransmission and muscle tone of the dog airway smooth muscle.

Abstract

SUMMARY1. The effects of epithelial cells were investigated on resting membrane potential and neuro-effector transmission in smooth muscle cells of the dog tracheal and bronchiolar tissues.2. The mean value of the resting membrane potential of the epithelium-intact bronchiolar smooth muscle cells of the dog was -700 + 1 mV (± S.D., n = 40) and mechanical denudation of the epithelial layer depolarized the membrane to -57 0 + 2'5 mV (± S.D., n = 40). Application of isolated and dispersed epithelial cells (> 2 x 105 cells/ml) to the perfusing solution repolarized the membrane of epithelium-denuded bronchiolar smooth muscle cells to -670 + 2-7 mV (± S.D., n = 20).The mean resting membrane potential of the mucosa-free tracheal smooth muscle cells was -59-1 + 1-4 mV (± S.D., n = 50), and application of isolated and dispersed cells (> 2 x 105 cells/ml) hyperpolarized the membrane to -67-2 + 1'8 mV (± S.D., n = 50). These repolarizing actions were not modified by indomethacin (10-5 M).3. In the epithelium-denuded bronchioles, ACh (> 10-9 M) dose-dependently depolarized the smooth muscle cells, while in the epithelium-intact bronchioles, ACh (10-11-10-8 M) did not affect the resting membrane potential. At a concentration of 10-7 M, ACh significantly depolarized the membrane.4. Electrical field stimulation (EFS; 50,ts in duration and about 10-20 V in strength) applied to ring preparations of the bronchioles evoked twitch-like contractions (hereafter referred as twitch contraction), and size of the twitch contractions gradually and continuously decreased in the presence or absence of indomethacin (10-5 M) and guanethidine (10-6 M). When similar experiments were performed using epithelium-denuded bronchiolar ring preparations, in no case was there a prominent reduction in the amplitude of the twitch contractions in the presence of indomethacin and guanethidine.5. The decremental response of the twitch contraction observed in the epitheliumintact bronchioles was overcome by application of the leukotriene synthesis inhibitor AA861 (10-6 M) and the leukotriene antagonist ON01078 (10-5 M).6. Leukotrienes C4 and D4 (LTC4 and LTD4, > 10-8 M) evoked muscle contraction with a steady increase in muscle tone, up to a certain level. However, at 10-9 M, LTC4 increased and LTD4 decreased the amplitude of the twitch contractions evoked by MS 9432

Cultured Epithelial Cells Release Cyclooxygenase-Dependent and Cyclooxygenase-lndependent Factors That Inhibit Cholinergic Contraction of Canine Airway Smooth Muscles

“…Some previous studies have suggested the possible existence of an EpDRF distinct from prostaglan dins [1,7,8,20,21], However, no study has demonstrated the existence of a cyclooxygenase-independent factor by using the supernatants from pure cultured epithelial cells. Our results using the supernatants suggest that epithelial cells can release transmissible compound(s) other than prostanoids.…”

“…is a candidate for the epithelium-derived relaxant factor (EpDRF) [10][11][12], PGE2 is the major product of the cyclooxygenase pathway released from epithelial cells in response to various stimuli, such as bradykinin [13] and leukotriene [14], It is well known that PGE2 inhibits the contraction of airway smooth muscle via pre-and post junctional mechanisms [15][16][17][18][19], However, much of the previous evidence for the inhibitory effect of epithelial cells on the contraction of smooth muscle has been obtained from preparations in which the epithelial cells were specifically stimulated, or simply denuded from the tissue. There have been very little data on whether epithe lial cells can release a sufficient amount of PGEi to sup press the contraction of smooth muscle in the absence of any stimuli [11], Other reports have indicated that the activity of EpDRF is unaffected or only partially inhibit ed by pretreatment with a cyclooxygenase inhibitor, and thus has implicated the existence of a noncyclooxygenase product [1,7,8,20,21]. The relative contribution of this noncyclooxygenase product to the inhibition of smooth muscle contraction is still uncertain.…”

Regional and species differences in glyburide‐sensitive K+ channels in airway smooth muscles as estimated from actions of KC 128 and levcromakalim

“…Moreover the basal 86Rb+ efflux from the bronchial smooth muscle tissues was also larger than that from the tracheal smooth muscle tissues. Xie et al (1992) reported that the resting a -601. membrane potential of the dog bronchiole with epithelium was higher than that without epithelium, and they postulated that a hyperpolarizing factor is released from the epithelial cells. The bronchial preparation we used in this study also had intact epithelial cells, so the higher resting membrane potential of bronchial smooth muscle cells may be due to an epithelial-drived hyperpolarizing factor that activates the K+ channels.…”

L-NAME-sensitive and -insensitive nonadrenergic noncholinergic relaxation of cat airway in vivo and in vitro

“…Small bronchi were used in the present experiments, since biphasic NANC relaxations could easily be evoked by EFS in the tissue [7]. Airway epithelium was carefully removed as much as possible by mechanical rubbing, according to a method described previously, since it is known that EFS stimulates airway epithelial cells to release factor(s) that induce the relaxation of dog bronchioles in the presence of indomethacin, atropine, guanethidine, and were precontracted with 5-HT (10 -5 M) [15]. The preparation was bathed in a modified Krebs solution of the following ionic concentrations (mM): Na + 137.4, K + 5.9, Mg 2+ 1.2, Ca 2+ 2.5, Cl -134.0, H 2 PO 4 -1.2, HCO 3 -15.5, and glucose 11.5.…”