Data from: The role of gravity in the evolution of mammalian blood pressure

Understanding of the factors involved in determining the level of central arterial blood pressure in mammals has been clouded by inappropriate allometric analyses that fail to account for phylogenetic relationships among species, and require pressure to approach 0 as body size decreases. The present study analyses systolic, mean arterial, and diastolic blood pressure in 47 species of mammal with phylogenetically informed techniques applied to two-parameter equations. It also sets non-linear, three-parameter equations to the data to remove the assumption of the two-parameter power equation that the smallest animals must have negligible blood pressure. These analyses show that blood pressure increases with body size. Non-linear analyses show that mean blood pressure increases from 93 mm Hg in a 10 g mouse to 156 mm Hg in a 4 tonne elephant. The scaling exponent of blood pressure is generally lower than, though not significantly different from, the exponent predicted on the basis of the expected scaling of the vertical distance between the head and the heart. This indicates that compensation for the vertical distance above the heart is not perfect and suggests that the pressure required to perfuse the capillaries at the top of the body may decrease in larger species.此前，学界对哺乳动物中枢动脉血压水平决定因素的认知始终被不当的异速分析（allometric analyses）所阻碍：此类分析未考虑物种间的系统发育关联（phylogenetic relationships），且默认当体型缩小时血压需趋近于0。本研究针对47种哺乳动物的收缩压、平均动脉压及舒张压，采用纳入系统发育信息的分析方法，并结合双参数幂方程（two-parameter power equation）开展分析。本研究同时通过非线性三参数方程拟合实验数据，以破除该双参数幂方程的预设假设——该假设认为体型最小的动物血压可忽略不计。上述分析结果表明，血压随体型增大而升高。非线性分析结果显示，平均动脉压从10克小鼠的93毫米汞柱（mm Hg）上升至4吨大象的156毫米汞柱。血压的异速缩放指数（scaling exponent）整体低于基于头心垂直距离预期缩放规律所预测的指数，但二者并无显著差异。这表明机体对心脏上方垂直距离的代偿并不完全，同时提示，体型更大的物种为灌注身体顶部毛细血管所需的血压可能有所降低。