Belik J
Department of Pediatrics, University of Manitoba, Winnipeg, Canada.
Can J Physiol Pharmacol. 1994 Nov;72(11):1464-8. doi: 10.1139/y94-211.
In the immediate neonatal period the pulmonary vascular resistance is higher than later in life. The role of maturational differences in the smooth muscle mechanical properties of large capacitance vessels in this response has not been previously studied. To this end, we studied the smooth muscle isometric and isotonic mechanical properties, as well as the myogenic response of large extralobar pulmonary arteries in newborn and adult guinea pigs. Compared with the adult, the newborn pulmonary vascular smooth muscle generates less force and has a similar shortening capacity but longer isometric and isotonic relaxation half times. The myogenic response could be elicited in 80% of the newborn and 70% of the adult vessels. A 20% increase in vessel diameter resulted in force generation equivalent to 46 +/- 5.1% of maximal isometric tension in the newborn. Such a response was significantly greater than observed for the adult vessels (14 +/- 2.8%; p < 0.001). Our results showed significant maturational differences in the mechanical properties of the large pulmonary artery smooth muscle in the newborn. We speculate that the presence of myogenic response in large pulmonary capacitance vessels and the observed greater magnitude of stretch-induced force generation in the newborn may play an important role in the maintenance of a higher pulmonary vascular resistance in the neonatal period.
在新生儿早期，肺血管阻力高于生命后期。大电容血管平滑肌力学特性的成熟差异在这种反应中的作用此前尚未得到研究。为此，我们研究了新生和成年豚鼠叶外大肺动脉的平滑肌等长和等张力学特性以及肌源性反应。与成年豚鼠相比，新生豚鼠肺血管平滑肌产生的力量较小，缩短能力相似，但等长和等张舒张半衰期更长。80%的新生血管和70%的成年血管可引发肌源性反应。血管直径增加20%时，新生豚鼠产生的力量相当于最大等长张力的46±5.1%。这种反应明显大于成年血管（14±2.8%；p<0.001）。我们的结果表明，新生豚鼠大肺动脉平滑肌的力学特性存在显著的成熟差异。我们推测，大肺电容血管中肌源性反应的存在以及新生豚鼠中观察到的更大程度的拉伸诱导力量产生可能在新生儿期维持较高肺血管阻力方面发挥重要作用。
