Holland R A, Rimes A F, Comis A, Tyndale-Biscoe C H
School of Physiology and Pharmacology, University of N.S.W., Sydney, Australia.
Respir Physiol. 1988 Jul;73(1):69-86. doi: 10.1016/0034-5687(88)90128-4.
Blood O2 transport and Hb type have been studied in pouch young and adult of a marsupial, the Tammar Wallaby. The O2-Hb equilibrium curves (at 35.5 degrees C and PCO2 = 34 Torr) had a high P50 in the first few days of life, up to 49 Torr. This fell to 32 Torr by 2 weeks of age. Also (delta log P50/delta PCO2) was low but it rose to adult levels by 2 weeks of age. The curves in these early pouch young showed a change in Hill coefficient (nH) at between 32 and 62% saturation, nH rising to more than 4.0 at higher O2 saturations. This indicates interaction between more than 4 Hb subunits. Model calculations showed that such curves could be produced by a mixture of 2 Hb components; one with a low P50 and low nH, and one with a high P50 and high nH. In this model the nH values were different from the nH values of either component. The temperature effect on P50 in early pouch young was higher than in adult Tammars and similar to that reported for adult eutherians. In the first 4 days all red cells were nucleated and four Hb types were present. Carbonic anhydrase activity in the blood before birth was about 30% of the adult levels. These levels remained until 2 days after birth, when a rapid rise in activity began, near-adult levels being reached at 5 days despite the animals being still very immature.
在有袋动物帚尾袋鼩的育儿袋幼崽和成年个体中，对血液氧气运输和血红蛋白类型进行了研究。氧气 - 血红蛋白平衡曲线（在35.5摄氏度和二氧化碳分压 = 34托时）在出生后的头几天具有较高的P50，高达49托。到2周龄时，这一数值降至32托。此外，（Δlog P50/Δ二氧化碳分压）较低，但到2周龄时升至成年水平。这些早期育儿袋幼崽的曲线在饱和度32%至62%之间显示出希尔系数（nH）的变化，在较高氧气饱和度下nH升至超过4.0。这表明超过4个血红蛋白亚基之间存在相互作用。模型计算表明，这样的曲线可以由两种血红蛋白成分的混合物产生；一种具有低P50和低nH，另一种具有高P50和高nH。在这个模型中，nH值与任何一种成分的nH值都不同。早期育儿袋幼崽中温度对P50的影响高于成年帚尾袋鼩，与成年真兽类动物的报道相似。在出生后的头4天，所有红细胞都有细胞核，并且存在四种血红蛋白类型。出生前血液中的碳酸酐酶活性约为成年水平的30%。这些水平一直保持到出生后2天，此时活性开始迅速上升，尽管动物仍然非常不成熟，但在5天时达到接近成年的水平。
