Shartau Ryan B, Baker Dan W, Brauner Colin J
Department of Zoology, University of British Columbia, Vancouver, BC, Canada.
Department of Fisheries and Aquaculture, Vancouver Island University, Nanaimo, BC, Canada.
J Comp Physiol B. 2017 Oct;187(7):985-994. doi: 10.1007/s00360-017-1065-x. Epub 2017 Mar 11.
White sturgeon (Acipenser transmontanus) completely protect intracellular tissue pH (pH) despite large reductions in extracellular (blood) pH (pH), termed preferential pH regulation, in response to elevated environmental PCO (hypercarbia) and in general appear to be relatively resilient to stressors. Preferential pH regulation is thought to be associated with hypercarbia tolerance in general, but has also recently been observed to protect pH against metabolic acidoses induced by exhaustive exercise and anoxia in a tropical air breathing catfish. We hypothesized that preferential pH regulation may also be a general strategy of acid-base regulation in sturgeon. To address this hypothesis, severe acidoses were imposed to reduce pH, and the presence or absence of preferential pH regulation was assessed in red blood cells (RBC), heart, brain, liver and white muscle. A respiratory acidosis was imposed using hyperoxia, while metabolic acidoses were induced by exhaustive exercise, anoxia or air exposure. Reductions in pH occurred following hyperoxia (0.15 units), exhaustive exercise (0.30 units), anoxia (0.10 units) and air exposure (0.35 units); all acidoses reduced RBC pH. Following hyperoxia, heart, brain and liver pH were preferentially regulated against the reduction in pH, similar to hypercarbia exposure. Following all metabolic acidoses heart pH was protected and brain pH remained unchanged following exhaustive exercise and air exposure, however, brain pH was reduced following anoxia. Liver and white muscle pH were reduced following all metabolic acidoses. These results suggest preferential pH regulation may be a general strategy during respiratory acidoses but during metabolic acidoses, the response differs between source of acidoses and tissues.
白鲟（Acipenser transmontanus）尽管细胞外（血液）pH值大幅降低，但能完全保护细胞内组织pH值，这被称为优先pH调节，以应对环境PCO升高（高碳酸血症），总体而言，白鲟似乎对压力源具有相对较强的恢复力。一般认为优先pH调节与高碳酸血症耐受性有关，但最近也观察到，在一种热带空气呼吸鲶鱼中，优先pH调节可保护pH值免受力竭运动和缺氧诱导的代谢性酸中毒影响。我们假设优先pH调节也可能是鲟鱼酸碱调节的一种普遍策略。为验证这一假设，通过施加严重酸中毒来降低pH值，并评估红细胞（RBC）、心脏、大脑、肝脏和白肌中优先pH调节的存在与否。使用高氧诱导呼吸性酸中毒，而力竭运动、缺氧或空气暴露则诱导代谢性酸中毒。高氧（0.15个单位）、力竭运动（0.30个单位）、缺氧（0.10个单位）和空气暴露（0.35个单位）后pH值均降低；所有酸中毒均降低了红细胞pH值。高氧后，心脏、大脑和肝脏的pH值优先调节以抵抗pH值降低，这与高碳酸血症暴露相似。所有代谢性酸中毒后，心脏pH值得到保护，力竭运动和空气暴露后大脑pH值保持不变，但缺氧后大脑pH值降低。所有代谢性酸中毒后肝脏和白肌的pH值均降低。这些结果表明，优先pH调节可能是呼吸性酸中毒期间的一种普遍策略，但在代谢性酸中毒期间，酸中毒来源和组织之间的反应有所不同。
