The roles of plasma accessible and cytosolic carbonic anhydrases in bicarbonate (HCO3 −) excretion in Pacific hagfish (Eptatretus stoutii)

AbstractPacific hagfish (Eptatretus stoutii) are marine scavengers and feed on decaying animal carrion by burrowing their bodies inside rotten carcasses where they are exposed to several threatening environmental stressors, including hypercapnia (high partial pressures of CO2). Hagfish possess a remarkable capacity to tolerate hypercapnia, and their ability to recover from acid –base disturbances is well known. To deal with the metabolic acidosis resulting from exposure to high CO2, hagfish can mount a rapid elevation of plasma HCO3− concentration (hypercarbia). OncePCO2 is restored, hagfish quickly excrete their HCO3− load, a process that likely involves the enzyme carbonic anhydrase (CA), which catalyzes HCO3− dehydration into CO2 at the hagfish gills. We aimed to characterize the role of branchial CA in CO2/HCO3− clearance from the plasma at the gills ofE. stoutii, under control and highPCO2 (hypercapnic) exposure conditions. We assessed the relative contributions of plasma accessible versus intracellular (cytosolic) CA to gill HCO3− excretion by measuring in situ [14C]-HCO3− fluxes. To accomplish this, we employed a novel surgical technique of individual gill pouch arterial perfusion combined with perifusion of the gill afferent to efferent water ducts. [14C]-HCO3− efflux was measured at the gills of fish exposed to control, hypercapnic (48  h) and recovery from hypercapnia conditions (6 h), in the presence of two well-known pharmacological inhibitors of...
Source: Journal of Comparative Physiology B: Biochemical, Systemic, and Environmental Physiology - Category: Physiology Source Type: research