Cooling-induced supersensitivity to acetylcholine in the isolated airway smooth muscle of the rat

Abstract

Isolated tracheal and bronchial strip-chain preparations of the rat were used to study the effect of temperature on electrically or acetylcholine-induced contraction. The preparations were suspended in the organ bath containing Krebs bicarbonate solution for isometric tension recording. A decrease of bath temperature from 37 degrees C to 20 degrees C (cooling) had no effect on basal tone but augmented the contractile responses of the trachea and bronchus caused by stimulation of intramural cholinergic nerves (0.5-5 Hz) or acetylcholine (3 mumol/l-0.3 mmol/l). Cooling-induced augmentation of the contractile response to acetylcholine was not affected by pretreatment of the tissue with physostigmine (0.1 mumol/l) or tetrodotoxin (0.3 mumol/l). The affinity of acetylcholine for the tracheal muscarinic receptors at 20 degrees C, determined from its dissociation constant (KA), was not significantly different from that at 37 degrees C. On the other hand, acetylcholine-induced contraction of trachea which was incubated with isosmotic K+- rich Krebs solution and with Ca-free, EGTA (0.1 mmol/l) containing Krebs solution were both augmented at 20 degrees C. Caffeine or vanadate, each at a lower concentration than the threshold for causing contraction by itself, augmented the contractile responses of the trachea to acetylcholine (1 mumol/l-0.3 mmol/l). These potentiating effects of caffeine and vanadate were greater at 20 degrees C then 37 degrees C. From these observations, it is concluded that increased responsiveness of the rat airway smooth muscle to acetylcholine with lowered temperature may involve the acceleration of Ca release from intracellular storage sites, inhibition of Ca extrusion from the cell and or the inhibition of Ca reuptake by intracellular storage sites.

The Effects of Vitamin E Treatment on Tracheal Reactivity and Some Biochemical Parameters in Diabetic Rats : Di̇yabeti̇k Siçanlarda, Vi̇tami̇n E Tedavi̇si̇ni̇n Trakeal Reakti̇vi̇te Ve Bazi Bi̇yoki̇msal Paramet

“…(19). Although we did not investigate the effect of diabetes on the binding characteristics of muscarinic receptors in rat trachea, the increased contractilities to ACh and KC1 in diabetic tracheas without any change in the sensitivity (pD 2 ) indicate that the hyper-responsiveness may be dependent to the alterations in (22,23,24). It has been shown that oxidative stress is responsible for the increased contractile responsiveness of diabetic vasculature by increasing diacylglycerol -protein kinase C (DAC-PKC) activity which stimulates IP 3 induced Ca +2 release from intracellular organelles leading to intracellular Ca +2 accumulation in diabetes mellitus (25,26).…”

The obligatory role of calcium in the development of antigen‐induced airway hyperreactivity to cold provocation in the rat isolated trachea

“…man, dog, guinea-pig and rat has been demonstrated to potentiate contractile responses to histamine, acetylcholine (ACh) or methacholine, etc. (Souhrada & Souhrada, 1981;Murlas et al, 1982;Tran et al, 1982;Ishii & Shimo, 1985). In the present study, the effect of antigen challenge on cold-induced responses in rat isolated tracheal segments was investigated.…”

Biphasic Relaxant Response of Ovine Trachealis Muscle to Electrical Field Stimulation: Influence of Cooling

“…The results showed that cooling of the airways can enhance or reduce agonistinduced contractions. Cholinergically induced contractility is enhanced in humans [1,2], rabbits [3], hamsters [4], rats [5], and dogs [6]. On the other hand, cholinergically induced contractility is reduced or unchanged in the guinea pig, depending on the agonist used.…”

“…Ishii and Shimo [5] reported that the increased contractions of the rat trachea to EFS are due to an enhanced sensitivity of the cholinoceptors to the neurotransmitter (acetylcholine). This was based on the fact that acetylcholine-induced (with or without cholinesterase inhibition) contractions of the rat trachea were similarly enhanced by cooling.…”

“…In their study, Ishii and Shimo [5] observed that cooling significantly enhanced electrically induced contractions in the rat trachea. These authors attributed the enhanced contractions to a cooling-induced increase in the affinity of the muscarinic receptors for acetylcholine.…”