West N H, Burggren W W
Respir Physiol. 1982 Feb;47(2):165-76. doi: 10.1016/0034-5687(82)90109-8.
Gill ventilation frequency (fG), the pressure amplitude (PBC) and stroke volume (VS) of buccal ventilation cycles, the frequency of air breaths (fL), water flow over the gills (VW), gill oxygen uptake (MGO2), oxygen utilization (U), and heart frequency (fH) have been measured in unanaesthetized, air breathing Rana catesbeiana tadpoles (stage XVI-XIX). The animals were unrestrained except for ECG leads or cannulae, and were able to surface voluntarily for air breathing. They were subjected to aquatic normoxia, hyperoxia and three levels of aquatic hypoxia, and their respiratory responses recorded in the steady state. The experiments were performed at 20 +/- 0.5 degrees C. In hyperoxia there was an absence of air breathing, and fG, PBC and VW fell from the normoxic values, while U increased, resulting in no significant change in MGO2. Animals in normoxia showed a very low fL which increased in progressively more hypoxic states. VW increased from the normoxic value in mild hypoxia (PO2 = 96 +/- 2 mm Hg), but fell, associated with a reduction in PBC, in moderate (PO2 = 41 +/- 1 mm Hg) and severe (PO2 = 21 +/- 3 mm Hg) hypoxia in the presence of lung ventilation. Gill MGO2 was not significantly different from the normoxic value in mild hypoxia but fell in moderate hypoxia, while in severe hypoxia oxygen was lost to the ventilating water from the blood perfusing the gills. There was no significant change in fH from the normoxic value in either hypoxia or hyperoxia. These data indicate, that in the bimodally breathing bullfrog tadpole, aquatic PO2 exerts a strong control over both gill and lung ventilation. Furthermore, there is an interaction between gill and lung ventilation such that the onset of a high frequency of lung ventilation in moderate and severe hypoxia promotes a suppression of gill ventilation cycles.
在未麻醉、能进行空气呼吸的牛蛙蝌蚪（第十六至十九阶段）中，测量了鳃通气频率（fG）、口腔通气周期的压力幅度（PBC）和每搏量（VS）、空气呼吸频率（fL）、鳃部水流（VW）、鳃部氧气摄取量（MGO2）、氧气利用率（U）以及心率（fH）。除了心电图导联或插管外，动物未受束缚，能够自主浮出水面进行空气呼吸。它们分别处于水生常氧、高氧和三种程度的水生低氧环境中，并记录其稳态下的呼吸反应。实验在20±0.5摄氏度下进行。在高氧环境中，空气呼吸消失，fG、PBC和VW低于常氧值，而U增加，导致MGO2无显著变化。处于常氧环境的动物fL非常低，在逐渐加重的低氧状态下增加。VW在轻度低氧（PO2 = 96±2毫米汞柱）时从常氧值增加，但在中度（PO2 = 41±1毫米汞柱）和重度（PO2 = 21±3毫米汞柱）低氧且存在肺通气时下降，同时PBC降低。轻度低氧时鳃部MGO2与常氧值无显著差异，但在中度低氧时下降，而在重度低氧时，灌注鳃部的血液中的氧气会散失到通气的水中。低氧或高氧环境下fH与常氧值均无显著变化。这些数据表明，在具有双重呼吸方式的牛蛙蝌蚪中，水生环境中的PO2对鳃和肺的通气均有强大的控制作用。此外，鳃和肺的通气之间存在相互作用，使得在中度和重度低氧时高频肺通气的开始会促进鳃通气周期的抑制。
