Smolich J J, Cox H S, Eisenhofer G, Esler M D
Institute of Reproduction and Development, Monash University, Clayton, Victoria, Australia.
Am J Physiol. 1997 Jul;273(1 Pt 1):L264-74. doi: 10.1152/ajplung.1997.273.1.L264.
To examine the pulmonary kinetics of the catecholamines norepinephrine and epinephrine immediately after birth, eight fetal lambs were instrumented with vascular catheters under general anesthesia at 133-134 days gestation (term = 147 days) and were delivered by cesarean section 1 wk later. Pulmonary norepinephrine and epinephrine kinetics were then studied 1 and 4 h after birth using radiotracer dilution methodology. The pulmonary fractional extraction of norepinephrine was similar in 1-h (0.111 +/- 0.021) and 4-h (0.117 +/- 0.023) lambs and constituted 24 +/- 5 and 32 +/- 9% of total body norepinephrine clearance, respectively. Pulmonary removal of epinephrine was less pronounced with a fractional extraction of 0.035 +/- 0.017 in 1-h and 0.036 +/- 0.013 in 4-h lambs, which corresponded to 8 +/- 4 and 9 +/- 3% of total body epinephrine clearance, respectively. Pulmonary spillover of norepinephrine into the circulation was similar in 1-h (79 +/- 26 ng.min-1.kg-1) and 4-h (82 +/- 18 ng.min-1.kg-1) lambs, and this comprised 27 +/- 8 and 42 +/- 8% of total body norepinephrine spillover, respectively. Pulmonary epinephrine spillover was not detectable at 1 h, but it occurred in all 4-h lambs, averaging 4.7 +/- 0.8 ng.min-1.kg-1 or 20 +/- 6% of epinephrine total body spillover. These findings indicate that the lungs of newborn lambs 1) are a major site for removal of norepinephrine and epinephrine from the circulation; 2) release a substantial quantity of norepinephrine into the circulation, consistent with the presence of tonic pulmonary sympathetic nerve activity; and 3) constitute a significant extra-adrenal source of plasma epinephrine.
为了研究出生后即刻儿茶酚胺去甲肾上腺素和肾上腺素在肺内的动力学变化，8只胎羊在妊娠133 - 134天（足月为147天）时接受全身麻醉，通过血管导管进行仪器植入，1周后行剖宫产分娩。然后在出生后1小时和4小时，使用放射性示踪剂稀释法研究肺内去甲肾上腺素和肾上腺素的动力学。出生后1小时（0.111±0.021）和4小时（0.117±0.023）的胎羊肺内去甲肾上腺素的分数提取率相似，分别占全身去甲肾上腺素清除率的24±5%和32±9%。出生后1小时（0.035±0.017）和4小时（0.036±0.013）的胎羊肺内肾上腺素的清除不太明显，分别占全身肾上腺素清除率的8±4%和9±3%。出生后1小时和4小时的胎羊肺内去甲肾上腺素向循环中的溢出量相似，分别为79±26 ng·min⁻¹·kg⁻¹和82±18 ng·min⁻¹·kg⁻¹，分别占全身去甲肾上腺素溢出量的27±8%和42±8%。出生后1小时未检测到肺内肾上腺素溢出，但在所有4小时的胎羊中均出现，平均为4.7±0.8 ng·min⁻¹·kg⁻¹，占肾上腺素全身溢出量的20±6%。这些发现表明，新生羔羊的肺：1）是循环中去甲肾上腺素和肾上腺素清除的主要部位；2）向循环中释放大量去甲肾上腺素，这与肺交感神经的紧张性活动一致；3）是血浆肾上腺素的一个重要肾上腺外来源。
