Günther B, Morgado E, Gonzalez U
Departamento de Fisiopatología, Facultad de Ciencias Biológicas, Universidad de Concepción, Chile.
Biol Res. 1993;26(3):341-55.
In homeotherms, the standardized (basal) metabolic rate should not be expressed per kilogram of body weight (specific metabolic rate), nor per unit of body surface (square meters of body-ambient interface), since both mitochondrial thermogenesis and heat-loss mechanisms (radiation, conduction, convection, evaporation) are not uniform processes. On the contrary, each organism is an heterogeneous bioreactor, which is composed at least of two compartments: 1) a metabolically active volume (aV), where oxidative phosphorylation takes place; and 2) a metabolically inactive volume (iV), where oxygen consumption is negligible. The ratio (aV/iV) is not invariant, since iV increases disproportionately with the scaling up of body size, and as shown by us, when the three main components of iV, i.e., skeleton, fat deposits, and blood volume, are added together, a similar disproportionality is found. The aV was determined by subtracting the iV from the total volume (V) of an organism, or by estimating the volume occupied by all mitochondria, or mitochondrial volume (mtV). For this purpose two procedures are discussed: 1) the stereological or morphometric method; and 2) the oxygen consumption per unit time or physiometric method. The latter procedure is based on the equivalence between an VO2 = 3 ml O2.min-1 and a mtV of 1 ml, whose oxidative phosphorylation yields an approximate power output of 1 watt. The correspondence between oxygen consumption, heat production, and electron flux at the respiratory chain of the mitochondrial cristae, is discussed. From a physical point of view, the metabolic rate is a "power" function (P = M L2T-3), where M = mass, L = length, and T = time. The dimensional analysis and the statistical treatment of the corresponding numerical values of more than 200 allometric equations yields the 3/4 power, law established by Kleiber (1961), for the relationship between basal metabolism and body weight. Instead of expressing the metabolic rate per unit body weight (kg-1) or per unit body surface (m-2) structural and functional criteria should be taken into account as, for instance, the distinction between iV and aV, and particularly by emphasizing the paramount importance of the mtV where oxidative phosphorylation takes place. An allometric equation relating mtV and body weight (W) could be tentatively established for interspecies comparisons.
在恒温动物中，标准化（基础）代谢率不应按每千克体重（比代谢率）或每单位体表面积（体-环境界面平方米）来表示，因为线粒体产热和散热机制（辐射、传导、对流、蒸发）并非均匀过程。相反，每个生物体都是一个异质生物反应器，至少由两个部分组成：1）代谢活跃体积（aV），发生氧化磷酸化的地方；2）代谢不活跃体积（iV），耗氧量可忽略不计的地方。比率（aV/iV）并非恒定不变，因为iV会随着体型增大而不成比例地增加，而且正如我们所表明的，当将iV的三个主要组成部分，即骨骼、脂肪沉积和血容量相加时，也会发现类似的不成比例情况。aV可通过从生物体总体积（V）中减去iV来确定，或者通过估算所有线粒体所占体积，即线粒体体积（mtV）来确定。为此讨论了两种方法：1）体视学或形态测量法；2）单位时间耗氧量或生理测量法。后一种方法基于VO2 = 3 ml O2·min-1与1 ml的mtV之间的等效性，其氧化磷酸化产生的近似功率输出为1瓦。讨论了线粒体嵴呼吸链处耗氧量、产热和电子通量之间的对应关系。从物理学角度来看，代谢率是一个“功率”函数（P = M L2T-3），其中M = 质量，L = 长度，T = 时间。对200多个异速生长方程的相应数值进行量纲分析和统计处理，得出了克莱伯（1961年）确立的3/4幂定律，用于描述基础代谢与体重之间的关系。不应按单位体重（kg-1）或单位体表面积（m-2）来表示代谢率，而应考虑结构和功能标准，例如iV和aV之间的区别，尤其要强调发生氧化磷酸化的mtV的至关重要性。可以尝试建立一个用于种间比较的、将mtV与体重（W）相关联的异速生长方程。
