Frappell P B, Mortola J P
School of Zoology, La Trobe University, Melbourne, Vic., Australia.
Respir Physiol. 2000 Mar;120(1):35-45. doi: 10.1016/s0034-5687(99)00103-6.
The Julia Creek dunnart (Sminthopsis douglasi) is a marsupial born after approximately 12 days of gestation. At birth, the newborn is approximately 4 mm long and weighs approximately 15 mg. Gaseous metabolism (oxygen consumption rate, V(O2), rate of carbon dioxide production, V(CO2) was measured separately across the airways (lungs) and the rest of the body (skin). At pouch temperature (36 degrees C) total V(O2) (i.e. skin + lungs) averaged 15 +/- 2 S.E.M. ml x kg(-1) x min(-1). At birth the skin contributed almost the total gaseous metabolism, and at 3 weeks approximately 1/3 of the total. The compliance of the respiratory system, per unit of body weight, was similar to that of other newborn mammals. During the first postnatal days breathing was an occasional event determined by gross body movements. Artificial expansion of the lungs temporarily stopped breathing, presumably a manifestation of the Hering-Breuer reflex. By the 2nd-3rd week breathing was regular, pulmonary ventilation (V(E)) averaged 263 ml x kg(-1) x min(-1), tidal volume (V(T)) 3.4 ml x kg(-1), breathing frequency (f) 87 breaths x min(-1). Lowering ambient temperature in steps from 36 to 20 degrees C reduced both lung and skin gaseous metabolism. V(E) and f, at first, were little affected but eventually they dropped in approximate proportion to metabolism, whereas V(T) remained unchanged. In conclusion, for the newborn dunnart gas exchange through the skin is a requirement because of the inefficient V(E). To what extent the V(E) adjustments to changes in metabolic rate reflect mechanisms of regulation remains unresolved.
朱莉娅溪袋鼬（史氏袋鼬）是一种有袋动物，妊娠期约为12天。出生时，新生袋鼬体长约4毫米，体重约15毫克。分别测量了通过气道（肺）和身体其他部位（皮肤）的气体代谢（氧气消耗率V（O₂）、二氧化碳产生率V（CO₂））。在育儿袋温度（36摄氏度）下，总V（O₂）（即皮肤 + 肺）平均为15±2标准误毫升×千克⁻¹×分钟⁻¹。出生时，皮肤几乎贡献了全部气体代谢，3周时约占总量的1/3。呼吸系统每单位体重的顺应性与其他新生哺乳动物相似。在出生后的头几天，呼吸是由身体的大幅度运动偶尔引发的。人工扩张肺部会暂时停止呼吸，这可能是黑林 - 布雷尔反射的一种表现。到第2 - 3周时呼吸变得规律，肺通气量（V（E））平均为263毫升×千克⁻¹×分钟⁻¹，潮气量（V（T））为3.4毫升×千克⁻¹，呼吸频率（f）为87次呼吸×分钟⁻¹。将环境温度从36摄氏度逐步降至20摄氏度会降低肺和皮肤的气体代谢。起初，V（E）和f受影响较小，但最终它们会大致按代谢率的比例下降，而V（T）保持不变。总之，对于新生袋鼬来说，由于肺通气效率低下，通过皮肤进行气体交换是必要的。肺通气量对代谢率变化的调整在多大程度上反映了调节机制仍未得到解决。
