Williams Terrie M, Zavanelli Mary, Miller Melissa A, Goldbeck Robert A, Morledge Michael, Casper Dave, Pabst D Ann, McLellan William, Cantin Lucas P, Kliger David S
Department of Ecology and Evolutionary Biology, Center for Ocean Health-Long Marine Laboratory, University of California at Santa Cruz, 100 Shaffer Road, Santa Cruz, CA 95060, USA.
Proc Biol Sci. 2008 Apr 7;275(1636):751-8. doi: 10.1098/rspb.2007.1484.
The vulnerability of the human brain to injury following just a few minutes of oxygen deprivation with submergence contrasts markedly with diving mammals, such as Weddell seals (Leptonychotes weddellii), which can remain underwater for more than 90 min while exhibiting no neurological or behavioural impairment. This response occurs despite exposure to blood oxygen levels concomitant with human unconsciousness. To determine whether such aquatic lifestyles result in unique adaptations for avoiding ischaemic-hypoxic neural damage, we measured the presence of circulating (haemoglobin) and resident (neuroglobin and cytoglobin) oxygen-carrying globins in the cerebral cortex of 16 mammalian species considered terrestrial, swimming or diving specialists. Here we report a striking difference in globin levels depending on activity lifestyle. A nearly 9.5-fold range in haemoglobin concentration (0.17-1.62 g Hb 100 g brain wet wt(-1)) occurred between terrestrial and deep-diving mammals; a threefold range in resident globins was evident between terrestrial and swimming specialists. Together, these two globin groups provide complementary mechanisms for facilitating oxygen transfer into neural tissues and the potential for protection against reactive oxygen and nitrogen groups. This enables marine mammals to maintain sensory and locomotor neural functions during prolonged submergence, and suggests new avenues for averting oxygen-mediated neural injury in the mammalian brain.
人类大脑在因溺水导致缺氧仅几分钟后就极易受伤，这与诸如威德尔海豹（Leptonychotes weddellii）等潜水哺乳动物形成了鲜明对比，威德尔海豹能在水下停留超过90分钟，且无神经或行为损伤。尽管其血氧水平与人类失去意识时相当，但仍会出现这种反应。为了确定这种水生生活方式是否会导致避免缺血缺氧性神经损伤的独特适应性变化，我们测量了16种被认为是陆生、游泳或潜水专家的哺乳动物大脑皮层中循环（血红蛋白）和驻留（神经球蛋白和细胞球蛋白）携氧球蛋白的含量。在此，我们报告了球蛋白水平因活动生活方式的不同而存在显著差异。陆生哺乳动物和深潜哺乳动物之间的血红蛋白浓度相差近9.5倍（0.17 - 1.62 g Hb 100 g脑湿重⁻¹）；陆生哺乳动物和游泳专家之间的驻留球蛋白相差三倍。这两类球蛋白共同为促进氧气向神经组织的转移以及抵御活性氧和氮基团提供了互补机制。这使得海洋哺乳动物在长时间潜水期间能够维持感觉和运动神经功能，并为避免哺乳动物大脑中氧介导的神经损伤提供了新途径。
