Pacific spiny dogfish (Squalus suckleyi) have been widely used as a representative species for chondrichthyan CO2 excretion. Pacific spiny dogfish have a slower red blood cell (RBC) carbonic anhydrase (CA) isoform than teleost fishes, extracellular CA activity, no endogenous plasma CA inhibitor, and plasma-accessible CA IV at the gills. Thus, both the RBC and plasma compartments contribute to bicarbonate ion (HCO3-) dehydration at the gills for CO2 excretion in contrast to teleost fishes, in which HCO3- dehydration is restricted to RBCs. We compared CA activity levels, subcellular localization, and presence of plasma CA inhibitors in the blood and gills of 13 chondrichthyans to examine the hypothesis that the dogfish model of CO2 excretion applies broadly to chondrichthyans. In general, blood samples from the 12 other chondrichthyans examined had lower RBC CA activity than teleosts, some extracellular CA activity, and no endogenous plasma CA inhibitor. While type IV-like membrane-associated CA was found in the gills in all four of the chondrichthyans examined, S. suckleyi had three times more CA activity (183±13.2 μmol CO2 min-1 mg protein-1) in the microsomal (membrane) fraction of gills than the other three. In addition, unexpected variation in CA characteristics was observed between chondrichthyan species. Thus, in general, it appears that the pattern of CA distribution in fishes can be generally categorized as either chondrichthyan or teleost models. However, further studies should examine the functional significance of the within-chondrichthyan differences we observed and investigate whether CO2 excretion patterns exist along a continuum or in discrete groups.

中文翻译：

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在Chondrichthyan CO2排泄模型的背景下，血液和G碳碳酸酐酶。

太平洋多刺dog鱼（Squalus suckleyi）已被广泛用作软骨鱼类CO 2排泄的代表性物种。太平洋带刺的dog鱼比硬骨鱼有较慢的红细胞（RBC）碳酸酐酶（CA）同种型，胞外CA活性，无内源性血浆CA抑制剂，plasma处血浆可及的CA IV。因此，与硬骨鱼不同，RBC和血浆室都对the处的碳酸氢根离子（HCO3-）脱水造成了CO2的排泄，而硬骨鱼类中的HCO3-脱水仅限于RBC。我们比较了13种软骨动物血液和g中的CA活性水平，亚细胞定位和血浆CA抑制剂的存在，以检验关于CO2排泄的狗鱼模型广泛适用于软骨动物的假说。一般来说，来自其他12个软骨鱼类的血液样本具有比硬骨鱼低的RBC CA活性，一些细胞外CA活性，并且没有内源性血浆CA抑制剂。尽管在所检查的全部四个软骨鱼类的the中都发现了IV型膜相关CA，但S.uckleyi在微粒体（膜）中的CA活性（183±13.2μmolCO2 min-1 mg蛋白-1）的三倍多。 ）fraction的比例要高于其他三个。此外，在软骨鱼类之间观察到了CA特征的意外变化。因此，通常看来，鱼类中CA分布的模式通常可以分为软骨鱼类模型或硬骨鱼类模型。然而，