Increased maximal pulmonary response to methacholine and airway smooth muscle in immature compared with mature rabbits.
Increased maximal pulmonary response to methacholine and airway smooth muscle in immature compared with mature rabbits.
复制标题
与成熟兔子相比，未成熟兔子对乙酰甲胆碱和气道平滑肌的最大肺部反应增加。
DOI：
10.1164/ajrccm.151.3.7881679
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Martin,JG
中科院分区：
文献类型：
--
作者：
Tepper,RS;Du,T;Styhler,A;Ludwig,M;Martin,JG
We compared the effect of maturation upon the maximal pulmonary response to inhaled methacholine in rabbits and also assessed whether there was an age-related difference in the quantity of airway smooth muscle. In sedated, paralyzed, and mechanically ventilated rabbits, pulmonary resistance was measured following increasing doses of aerosolized methacholine (0.5 to 256 mg/ml). The six mature rabbits (6 mo) demonstrated a plateau in their dose-response curves whereas only three of six immature animals (1 mo) had a plateau. The immature compared with the mature animals had a greater maximal increase in pulmonary resistance (950% versus 380%). The lungs were examined by light microscopy to determine morphometrically the area of smooth muscle (ASM) in the airway walls. ASM was normalized for airway size by dividing by the ideal airway area. The normalized ASM was different for the two age groups and the immature animals' airways had more smooth muscle. The relationship between airway size and ASM was similar for the two age groups with smaller airways having proportionately more smooth muscle. The differences with age in ASM area were primarily due to the immature animals having a greater number of airways of small size. There was not a significant relationship between the maximal percent increase in pulmonary resistance and the normalized ASM. We conclude that inhaled methacholine produces a greater maximal increase in the pulmonary resistance of immature than mature rabbits and that this difference is unlikely to be caused by a proportionately greater quantity of ASM in the immature than the mature rabbit airways. Tepper RS, Du T, Styhler A, Ludwig M, Martin JG. Increased maximal pulmonary response to methacholine and airway smooth muscle in immature compared with mature rabbits. Am J Respir Crit Care Med 1995; 151: 836-40.Nonasthmatic adults can inhale very large doses of the bronchoconstricting agonists, methacholine or histamine, with only a small reduction in pulmonary function (1-4). In addition, their doseresponse curves demonstrate a maximal response or plateau with larger doses producing no further decline in pulmonary function. In contrast to adults, normal infants demonstrate marked reductions in pulmonary function at low doses of methacholine or histamine and the maximal response can not be assessed because testing is limited by the development of significant airway obstruction and respiratory symptoms (5-7). Although an increase in sensitivity to inhaled agonists is frequently associated with an exaggerated maximal response, these two components of the pulmonary response may be independently determined (4, 8). In vitro, several animal species demonstrate age-related differences of air-
