Abstract：
Adipose tissue has many important functions including metabolic energy storage, endocrine functions, thermoregulation and structural support. Given these varied functions, the microvascular characteristics within the tissue will have important roles in determining rates/limits of exchange of nutrients, waste, gases and molecular signaling molecules between adipose tissue and blood. Studies on skeletal muscle have suggested that tissues with higher aerobic capacity contain higher microvascular density (MVD) with lower diffusion distances (DD) than less aerobically active tissues. However, little is known about MVD in adipose tissue of most vertebrates; therefore, we measured microvascular characteristics (MVD, DD, diameter and branching) and cell size to explore the comparative aerobic activity in the adipose tissue across diving tetrapods, a group of animals facing additional physiological and metabolic stresses associated with diving. Adipose tissues of 33 animals were examined, including seabirds, sea turtles, pinnipeds, baleen whales and toothed whales. MVD and DD varied significantly (P < 0.001) among the groups, with seabirds generally having high MVD, low DD and small adipocytes. These characteristics suggest that microvessel arrangement in short duration divers (seabirds) reflects rapid lipid turnover, compared to longer duration divers (beaked whales) which have relatively lower MVD and greater DD, perhaps reflecting the requirement for tissue with lower metabolic activity, minimizing energetic costs during diving. Across all groups, predictable scaling patterns in MVD and DD such as those observed in skeletal muscle did not emerge, likely reflecting the fact that unlike skeletal muscle, adipose tissue performs many different functions in marine organisms, often within the same tissue compartment.
摘要：
脂肪组织具有许多重要功能，包括代谢能量储存，内分泌功能，温度调节和结构支持。鉴于这些不同的功能，组织内的微血管特征将在确定营养交换的速率/限制方面具有重要作用，废物,脂肪组织和血液之间的气体和分子信号分子。对骨骼肌的研究表明，与需氧活性较低的组织相比，有氧能力较高的组织含有较高的微血管密度（MVD）和较低的扩散距离（DD）。然而,对大多数脊椎动物脂肪组织中的MVD知之甚少；因此，我们测量了微血管特征(MVD，DD,直径和分支）和细胞大小，以探索潜水四足动物脂肪组织中的比较有氧活动，一组面临与潜水相关的额外生理和代谢压力的动物。检查了33只动物的脂肪组织，包括海鸟,海龟,针脚,须鲸和齿鲸.MVD和DD组间差异显著(P<0.001),海鸟的MVD通常很高，低DD和小脂肪细胞。这些特征表明，短时间潜水员（海鸟）的微血管排列反映了快速的脂质周转，与持续时间较长的潜水员（喙鲸）相比，MVD相对较低，DD较大，也许反映了对代谢活性较低的组织的需求，在潜水过程中最大限度地减少能量成本。在所有团体中，MVD和DD中可预测的缩放模式，如在骨骼肌中观察到的模式，没有出现，很可能反映出与骨骼肌不同的事实，脂肪组织在海洋生物中执行许多不同的功能，通常在同一组织室内。
