Department of Biology, Portland State University, Portland, OR 97207-0751, USA.
J Exp Biol. 2010 Nov 1;213(Pt 21):3710-6. doi: 10.1242/jeb.048504.
Rhinella marina and Lithobates catesbeianus have known differences in the capacity to mobilize lymph to stabilize blood volume following dehydration and hemorrhage. The purpose of these experiments was to assess whether there are interspecific differences in basic lymph heart functions. The end diastolic volumes of posterior lymph hearts averaged 10.8 μl kg⁻¹ in R. marina and 7.9-10.8 μl kg⁻¹ in L. catesbeianus by conductance manometry, and 9-32 μl kg⁻¹ in R. marina by ultrasound techniques, which correlated with body mass. Stroke volumes were approximately 20% of end diastolic volumes in both species. Peak systolic pressures and stroke work were correlated with the index of contractility (dP/dt(max)) in both species. Stroke volume was correlated to stroke work but not peak systolic pressure, end diastolic volume or end diastolic pressure indicating the preload variables do not seem to determine stroke volume as would be predicted from Starling considerations of the blood heart. Renal portal elastance (end systolic pressure/stroke volume) an afterload index did not differ interspecifically, and was equivalent to values for systemic flow indices from mice of equivalent ventricular volume. These data, taken together with predictions derived from mammalian models on the effect of high resistance indicate afterload (renal portal pressure), may be important determinants of posterior lymph heart stroke volume. The shape of the pressure-volume loop is different from an idealized version previously reported, and is influenced by end diastolic volume. Our data indicate that increasing end diastolic pressure and volume can influence the loop shape but not the stroke volume. This indicates that lymph hearts do not behave in a Starling Law manner with increased preload volume.
拉氏蟾蜍和牛蛙在后勒氏心脏脱水和出血后，在动员淋巴液以稳定血容量的能力上存在已知差异。这些实验的目的是评估是否存在种间后勒氏心脏基本功能的差异。通过导纳法测量，拉氏蟾蜍的后勒氏心脏舒张末期容积平均为 10.8 μl kg⁻¹，牛蛙为 7.9-10.8 μl kg⁻¹，而通过超声技术测量，拉氏蟾蜍的后勒氏心脏舒张末期容积为 9-32 μl kg⁻¹，这与体重相关。两种动物的每搏量均约为舒张末期容积的 20%。两种动物的收缩压峰值和每搏功均与收缩性指数（dP/dt(max)）相关。每搏量与每搏功相关，但与收缩压峰值、舒张末期容积或舒张末期压力无关，这表明前负荷变量似乎并不像从血液心脏的 Starling 考虑中预测的那样决定每搏量。后负荷指数（收缩压/每搏量）——肾门静脉弹性，种间无差异，与等效心室容积的小鼠系统流量指数的数值相当。这些数据与从哺乳动物模型得出的关于高阻力对后勒氏心脏每搏量影响的预测一起表明，后负荷（肾门静脉压力）可能是后勒氏心脏每搏量的重要决定因素。压力-容积环的形状与之前报道的理想化版本不同，并且受到舒张末期容积的影响。我们的数据表明，增加舒张末期压力和容积会影响环的形状，但不会影响每搏量。这表明，淋巴心脏不会像 Starling 定律那样随着前负荷容积的增加而产生变化。
