Abstract：
The presence of cardiac shunts in ectothermic tetrapods is thought to be consistent with active vascular modulations for proper hemodynamic support. Local control of blood flow modulates tissue perfusion and thus systemic conductance (Gsys) is assumed to increase with body temperature (Tb) to accommodate higher aerobic demand. However, the general increase of Gsys presses for a higher right-to-left (R-L) shunt, which reduces arterial oxygen concentration. In contrast, Tb reduction leads to a Gsys decrease and a left-to-right shunt, which purportedly increases pulmonary perfusion and plasma filtration in the respiratory area. This investigation addressed the role of compensatory vascular adjustments in the face of the metabolic alterations caused by Tb change in the South American rattlesnake (Crotalus durissus). Cardiovascular recordings were performed in decerebrated rattlesnake preparations at 10, 20 and 30°C. The rise in Tb increased metabolic demand, and correlated with an augmentation in heart rate. Although cardiac output increased, systemic stroke volume reduced while pulmonary stroke volume remained stable. Although that resulted in a proportionally higher increase in pulmonary blood flow, the R-L shunt was maintained. While the systemic compliance of large arteries was the most relevant factor in regulating arterial systemic blood pressure, peripheral conductance of pulmonary circulation was the major factor influencing the final cardiac shunt. Such dynamic adjustment of systemic compliance and pulmonary resistance for shunt modulation has not been demonstrated before and contrasts with previous knowledge on shunt control.
摘要：
在放热四足动物中存在心脏分流器被认为与主动血管调节以获得适当的血液动力学支持是一致的。血流的局部控制调节组织灌注,因此假定全身电导(Gsys)随着体温(Tb)而增加以适应更高的需氧需求。然而,Gsys压力的一般增加为更高的右向左(R-L)分流，降低动脉血氧浓度.相比之下,Tb减少导致Gsys减少和左向右分流，据称，这增加了肺灌注和呼吸区域的血浆过滤。这项研究探讨了代偿性血管调整在面对南美响尾蛇（Crotalusdurisus）Tb变化引起的代谢改变中的作用。在10、20和30°C下，在去循环响尾蛇制剂中进行心血管记录。Tb的上升增加了代谢需求，并与心率的增加有关。虽然心输出量增加,全身每搏输出量减少，而肺每搏输出量保持稳定。尽管这导致肺血流量成比例地增加，R-L分流维持。虽然大动脉的全身顺应性是调节动脉全身血压的最相关因素，肺循环外周电导是影响最终心脏分流的主要因素。之前尚未证明过这种动态调整系统顺应性和肺阻力以进行分流调节，并且与先前关于分流控制的知识形成对比。
