Ramchandani R, Shen X, Gunst S J, Tepper R S
Department of Pediatrics, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
J Appl Physiol (1985). 2003 Jul;95(1):265-71. doi: 10.1152/japplphysiol.00362.2002.
Immature rabbits have greater maximal airway narrowing with bronchoconstriction in vivo compared with mature animals. As isolated immature lungs have a lower shear modulus, it is unclear whether the greater airway narrowing in the immature lung is secondary to less tethering between the airways and the lung parenchyma or to differences in the mechanical properties of the mature and immature airways. In the present study, we compared the mechanical properties of fluid-filled, isolated, intraparenchymal airway segments of the same generation from mature and immature rabbits. Stimulation with ACh resulted in greater airway narrowing in immature than mature bronchi. The immature bronchi were more compliant, had a lower resting airway volume, and were more collapsible compared with the mature bronchi. When the airways were contracted with ACh under isovolume conditions, the immature bronchi generated greater active pressure, and they were more sensitive to ACh than were mature bronchi. Our results suggest that maturational differences in the structure and function of the airways in the absence of the lung parenchyma can account for the greater maximal narrowing of immature than mature airways in vivo.
与成熟动物相比，未成熟兔在体内支气管收缩时气道最大狭窄程度更大。由于离体未成熟肺的剪切模量较低，尚不清楚未成熟肺中更大的气道狭窄是继发于气道与肺实质之间的固定较少，还是由于成熟和未成熟气道机械性能的差异。在本研究中，我们比较了来自成熟和未成熟兔同一代的充满液体、离体的实质内气道节段的机械性能。用乙酰胆碱刺激导致未成熟支气管比成熟支气管出现更大的气道狭窄。与成熟支气管相比，未成熟支气管更顺应性，静息气道容积更低，且更易塌陷。当气道在等容条件下用乙酰胆碱收缩时，未成熟支气管产生更大的主动压力，并且它们比成熟支气管对乙酰胆碱更敏感。我们的结果表明，在没有肺实质的情况下，气道结构和功能的成熟差异可以解释未成熟气道在体内比成熟气道更大的最大狭窄程度。
