title: Hypertonic and isotonic potassium solutions have different effects on vessel contractility resulting in differences in optimal resting tension in rat aorta.
abstract: OBJECTIVE
  To compare high K(+ )-induced contraction and optimal resting tension measured by two commonly used techniques of hypertonic and isotonic K(+ ) in aortas with and without adventitial fat from various age rats.
  
  
  METHODS
  Three age groups of rats (15, 25, and 62 weeks) were used to prepare thoracic aortic rings in which adventitial fat was either removed or left intact. High K(+ ) (30 mmol/L)-induced contractions were observed under increasing resting tensions of 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 g. Optimal resting tension was the resting tension at which the aorta showed a maximal contraction.
  
  
  RESULTS
  The contractions induced by 2 kinds of high K(+ ) were significantly different. Hypertonic and isotonic K(+ ) induced a different style of contraction, and the pattern varied with different ages. At the age of 15 weeks, isotonic K(+ )-induced contractions were greater than hypertonic K+-induced contractions. However, at the age of 62 weeks, isotonic K(+ )-induced contractions were smaller than hypertonic K(+ )-induced contractions. Optimal resting tensions measured by 2 kinds of high K(+ ) were inconsistent. Optimal resting tensions in different kinds of aortic preparations from various age rats were almost a constant of 2 g, determined by isotonic K(+ ), but a variable, determined by hypertonic K(+ ). The adventitial fat could delay the development of high K(+ )-induced contractions at different resting tensions, but had little effect on the maximal contractions.
  
  
  CONCLUSIONS
  Hypertonic and isotonic K(+ ) may produce different contractions resulting in differences in optimal resting tension in rat aorta.
authors: Department of Pharmacology, Second Military Medical University, Shanghai 200433, China.
authors: Yun-Feng
authors: YF
authors: Guan
authors: Ruo-Hua
authors: RH
authors: Chen
authors: Pei
authors: P
authors: Wang
authors: Ye
authors: Y
authors: Qin
authors: Ding-Feng
authors: DF
authors: Su
authors: Chao-Yu
authors: CY
authors: Miao
mesh_terms: D000367:Age Factors; D000818:Animals; D001011:Aorta / Q000033:anatomy & histology / Q000187:drug effects / Q000502:physiology; D006982:Hypertonic Solutions / Q000494:pharmacology*; D007552:Isotonic Solutions / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009129:Muscle Tonus / Q000187:drug effects* / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
chemical_list: D006982:Hypertonic Solutions; D007552:Isotonic Solutions; D011188:Potassium