Department of Biomedical Sciences, College of Nursing, Public Authority for Applied Education & Training, P.O.Box 293, Shuwaikh Housing, Kuwait.
J Therm Biol. 2021 Jan;95:102818. doi: 10.1016/j.jtherbio.2020.102818. Epub 2021 Jan 5.
The mechanism of cooling-induced response of smooth muscles remains little understood despite the increasing importance given to it in recent years. The aim of this study was to examine the possibility of releasing a relaxant or a contractile substance during cooling from vascular and non-vascular smooth muscles.
Assessing the effect of cooling for two different smooth muscles together, vascular (aorta or carotid) which induced relaxation, and non-vascular (jejunum or bladder) which induced contraction. Hanging a pair of smooth muscle strips from different body organs in the same organ bath filled with Krebs solution, each strip was connected to its own transducer and recorder and stepwise cooling was applied. Recordings of isometric tension using organ-bath techniques.
Step-wise cooling (37 °C-4 °C) of aorta and carotid smooth muscle preparations induced reproducible graded relaxation while jejunum and bladder preparations induced reproducible graded tonic contractions, inversely proportional to temperature. The responses of all the smooth muscle preparations were the same magnitude either alone or as a pair in the organ bath. Cooling abolished rhythmic smooth muscle activity of jejunum and bladder. Cooling-induced contraction was reduced by incubation in Ca-free solution. The effect of cooling either relaxation or contraction was not enhanced or attenuated by the presence of the two different smooth muscles with opposite response in the same organ bath, proving the absence of a relaxant or a contractile substance released during cooling.
Cooling of aorta and carotid artery induced relaxation while jejunum and bladder induced contraction. The response to cooling is inversely proportional to the temperature. There was neither a relaxant nor a contractile substance released from vascular or non-vascular smooth muscles during cooling. Our study suggested that the effect of cooling is through a thermal receptor with two subtype one in the vascular smooth muscle (deep blood vessels) which induces relaxation, and the second in non-vascular smooth muscles (non-vascular organs) that induces contraction and the responses depend on extracellular calcium.
尽管近年来人们对其越来越重视，但平滑肌冷却反应的机制仍知之甚少。本研究旨在探讨在从血管和平滑肌中冷却时是否可能释放松弛或收缩物质。
同时评估两种不同平滑肌（引起松弛的血管（主动脉或颈动脉）和引起收缩的非血管（空肠或膀胱））冷却时的作用。将一对来自不同器官的平滑肌条悬挂在充满 Krebs 溶液的同一器官浴中，每个条带都连接到自己的换能器和记录器，并逐步冷却。使用器官浴技术记录等长张力。
逐步冷却（37°C-4°C）主动脉和颈动脉平滑肌制剂可引起可重复的分级松弛，而空肠和膀胱制剂可引起可重复的分级紧张收缩，与温度成反比。所有平滑肌制剂的反应在器官浴中无论是单独还是成对，其幅度都相同。冷却消除了空肠和膀胱的节律性平滑肌活动。在无钙溶液中孵育可减少冷却诱导的收缩。在同一器官浴中存在具有相反反应的两种不同平滑肌的情况下，冷却的作用（无论是松弛还是收缩）既没有增强也没有减弱，证明在冷却过程中没有释放松弛或收缩物质。
冷却主动脉和颈动脉引起松弛，而冷却空肠和膀胱引起收缩。对冷却的反应与温度成反比。在冷却过程中，血管或非血管平滑肌既没有释放松弛剂也没有释放收缩剂。我们的研究表明，冷却的作用是通过一种热受体，一种在血管平滑肌（深部血管）中引起松弛的亚型，另一种在非血管平滑肌（非血管器官）中引起收缩的亚型，而反应取决于细胞外钙。
