Tunnah Louise, Robertson Cayleih E, Turko Andy J, Wright Patricia A
Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
Department of Integrative Biology, University of Guelph, Guelph, Ontario N1G 2W1, Canada; Department of Biology, McMaster University, Hamilton, Ontario L8S 4K1, Canada.
Comp Biochem Physiol A Mol Integr Physiol. 2021 Feb;252:110848. doi: 10.1016/j.cbpa.2020.110848. Epub 2020 Nov 17.
When the amphibious mangrove rivulus (Kryptolebias marmoratus) leaves water for extended periods, hemoglobin-O binding affinity increases. We tested the hypothesis that the change in affinity was a consequence of hemoglobin isoform switching driven by exposure to environments associated with increased internal CO levels. We exposed K. marmoratus to either water (control, pH 8.1), air, aquatic hypercarbia (5.1 kPa CO, pH 6.6-6.8), or aquatic acid (isocarbic control, pH 6.6-6.8), for 7 days, and measured hemoglobin-O affinity spectrophotometrically. We found that mangrove rivulus compensated for elevated CO and aquatic acid exposure by shifting hemoglobin-O affinity back to aquatic (control) levels when measured at an ecologically-relevant high CO level that would be experienced in vivo. Using proteomics, we found that the hemoglobin subunits present in the blood did not change between treatments, but air and aquatic acid exposure altered the abundance of cathodic hemoglobin subunits. We therefore conclude that hemoglobin isoform switching is not a primary strategy used by mangrove rivulus to adjust P under these conditions. Abundances of other RBC proteins also differed between treatment groups relative to control fish (e.g. Rhesus protein type A, band 3 anion exchanger). Overall, our data indicate that both aquatic hypercarbia and aquatic acidosis create similar changes in hemoglobin-O affinity as air exposure. However, the protein-level consequences differ between these groups, indicating that the red blood cell response of mangrove rivulus can be modulated depending on the environmental cue received.
当两栖的红树鳉（Kryptolebias marmoratus）长时间离开水时，血红蛋白与氧气的结合亲和力会增加。我们测试了这样一种假设，即亲和力的变化是由于暴露于与体内二氧化碳水平升高相关的环境中所驱动的血红蛋白亚型转换的结果。我们将红树鳉暴露于水（对照，pH 8.1）、空气、水生高碳酸血症（5.1 kPa二氧化碳，pH 6.6 - 6.8）或水生酸（等碳酸对照，pH 6.6 - 6.8）中7天，并通过分光光度法测量血红蛋白与氧气的亲和力。我们发现，当在体内会经历的生态相关高二氧化碳水平下测量时，红树鳉通过将血红蛋白与氧气的亲和力恢复到水生（对照）水平，来补偿升高的二氧化碳和水生酸暴露。使用蛋白质组学方法，我们发现不同处理之间血液中存在的血红蛋白亚基没有变化，但空气和水生酸暴露改变了阴极血红蛋白亚基的丰度。因此，我们得出结论，在这些条件下，血红蛋白亚型转换不是红树鳉用来调节氧气亲和力的主要策略。相对于对照鱼，其他红细胞蛋白的丰度在不同处理组之间也存在差异（例如恒河猴A型蛋白、带3阴离子交换蛋白）。总体而言，我们的数据表明，水生高碳酸血症和水生酸中毒与空气暴露一样，会使血红蛋白与氧气的亲和力产生类似的变化。然而，这些组之间在蛋白质水平上的结果有所不同，这表明红树鳉的红细胞反应可以根据所接收的环境信号进行调节。
