Lillywhite H B, Gallagher K P
J Exp Zool. 1985 Sep;235(3):325-34. doi: 10.1002/jez.1402350303.
Radioactively-labeled microspheres were used to quantify adjustments of regional blood flows in 15 snakes (Elaphe obsoleta) subjected to 45 degrees head-up tilt. Heart rate and peripheral vascular resistance increased during tilt to compensate for the passive drop of pressure at the head. Two snakes failed to regulate blood pressure, but in 13 others arterial pressure increased at midbody (where passive changes in pressure are unexpected due to tilt alone) and arterial pressure at the head averaged 67% of the pretilt value. Tissue blood flow was reduced significantly in visceral organs, posterior skin and posterior skeletal muscle, but was maintained at pretilt levels in brain, heart, lung and anterior tissues. Ventricular systemic output averaged 24 ml/min X kg in horizontal posture and 9.4 ml/min X kg during tilt. Comparable values for pulmonary output were 4 and 6.5 ml/min X kg. Patterns of intraventricular shunting of blood acted to maintain pulmonary flow during tilt. A large right-to-left shunt (mean 76%) was present in horizontal snakes, but the shunted fraction declined during tilt (mean 54%). Left-to-right shunt increased during tilt from 7% to 14%.
放射性标记的微球被用于量化15条受到45度头高位倾斜的蛇（王锦蛇）局部血流的调整情况。倾斜过程中心率和外周血管阻力增加，以补偿头部压力的被动下降。两条蛇未能调节血压，但在其他13条蛇中，身体中部的动脉压升高（仅因倾斜，此处压力不应出现被动变化），头部的动脉压平均为倾斜前值的67%。内脏器官、后部皮肤和后部骨骼肌的组织血流显著减少，但脑、心脏、肺和前部组织的血流维持在倾斜前水平。水平姿势下心室系统输出平均为24毫升/分钟×千克，倾斜时为9.4毫升/分钟×千克。肺输出的相应值分别为4和6.5毫升/分钟×千克。倾斜过程中，心室内血液分流模式起到维持肺血流的作用。水平状态的蛇存在较大的右向左分流（平均76%），但倾斜过程中分流比例下降（平均54%）。倾斜过程中左向右分流从7%增加到14%。
