Red blood cell carbonic anhydrase mediates oxygen delivery via the Root effect in red drum

  title={Red blood cell carbonic anhydrase mediates oxygen delivery via the Root effect in red drum},
  author={Angelina M. Dichiera and A. Esbaugh},
  journal={Journal of Experimental Biology},
ABSTRACT Oxygen (O2) and carbon dioxide (CO2) transport are tightly coupled in many fishes as a result of the presence of Root effect hemoglobins (Hb), whereby reduced pH reduces O2 binding even at high O2 tensions. Red blood cell carbonic anhydrase (RBC CA) activity limits the rate of intracellular acidification, yet its role in O2 delivery has been downplayed. We developed an in vitro assay to manipulate RBC CA activity while measuring Hb-O2 offloading following a physiologically relevant CO2… Expand
2 Citations
Contrasting strategies of hypoxic cardiac performance and metabolism in cichlids and armoured catfish.
The heart of tropical fishes is a particularly useful model system in which to investigate mechanisms of hypoxic tolerance and maintenance of heart performance under hypoxia may relate to a tradeoff between air breathing via a modified stomach and circulatory demands for digestion. Expand
Is hypoxia vulnerability in fishes a by-product of maximum metabolic rate?
Evidence that O2 supply capacity is not constant in all fishes is provided, with some species exhibiting an elevated O1 supply capacity in hypoxic environments and the divergent selective pressures on hypoxia- and exercise-based cardiorespiratory adaptations in fishes are discussed. Expand


Plasma-accessible carbonic anhydrase at the tissue of a teleost fish may greatly enhance oxygen delivery: in vitro evidence in rainbow trout, Oncorhynchus mykiss
If plasma-accessible CA-mediated short-circuiting is operational in vivo, the combined Bohr-Root effect system unique to teleost fishes could markedly enhance tissue O2 delivery far in excess of that in vertebrates possessing a Bohr effect alone and may lead to insights about the early evolution of the Root effect. Expand
The importance of a single amino acid substitution in reduced red blood cell carbonic anhydrase function of early-diverging fish
Data indicate that low-activity RBC CA may be present in all fish with branchial CA-IV, and that the high-activityRBC CA seen in most teleosts may have evolved in conjunction with enhanced hemoglobin pH sensitivity. Expand
Beyond just hemoglobin: Red blood cell potentiation of hemoglobin-oxygen unloading in fish.
Although data are limited, these attributes may be general characteristics of teleosts and the generation and elimination of pH disequilibrium states at the RBC will likely enhance Hb-O2 unloading to some degree in other vertebrates. Expand
Root Effect Hemoglobin May Have Evolved to Enhance General Tissue Oxygen Delivery
It is reported that when rainbow trout are exposed to elevated water carbon dioxide, red muscle partial pressure of oxygen (PO2) increases by 65%—evidence that Root hemoglobins enhance general tissue O2 delivery during acidotic stress, and argues that CA activity in muscle capillaries short-circuits red blood cell (RBC) pH regulation. Expand
The O2 and CO2 Transport System in Teleosts and the Specialized Mechanisms That Enhance Hb–O2 Unloading to Tissues
A novel mechanism of enhanced Hb–O2 unloading in teleosts is described and discussed, one that relies on the heterogeneous distribution of plasma-accessible carbonic anhydrase (PACA), an intrinsic characteristic of the cardiovascular system, and a vastly understudied area not only in fishes. Expand
Evidence for a plasma-accessible carbonic anhydrase in the lumen of salmon heart that may enhance oxygen delivery to the myocardium
Results from research in coho salmon support the presence of an enhanced oxygen delivery system in the lumen of a salmonid heart, which could help support cardiac function when oxygen supply to this vital organ becomes limiting. Expand
Time course of red blood cell intracellular pH recovery following short-circuiting in relation to venous transit times in rainbow trout, Oncorhynchus mykiss.
Teleosts have evolved a system that greatly enhances O2 unloading from pH-sensitive Hb at the tissues, while protecting O2 loading at the gills; the resulting increase in O2 transport per unit of blood flow may enable the tremendous athletic ability of salmonids. Expand
Regulation of blood oxygen transport and red cell pHi after exhaustive activity in rainbow trout (Salmo gairdneri) and starry flounder (Platichthys stellatus).
In vitro, exogenous adrenaline reduced the Bohr and Root shifts caused by elevated PaCO2 and depressed plasma pH in rainbow trout blood, but not in starry flounder blood, and the observation that catecholamines did not affect the in vitro blood--O2 dissociation curve, suggests that additional factors may be involved in regulating O2 transport after exercise inFlounder. Expand
Functional support for a novel mechanism that enhances tissue oxygen extraction in a teleost fish
Results show that maximal exercise performance in salmon, and thus a successful spawning migration, may not be possible without paCA, and the recruitment of paCA was plastic and increased following hypoxic acclimation. Expand
A unique mode of tissue oxygenation and the adaptive radiation of teleost fishes
It is suggested that this unique mode of tissue O2 transfer evolved in the Triassic/Jurassic Period, when O2 levels were low, ultimately giving rise to the most extensive adaptive radiation of extant vertebrates, the teleost fishes. Expand