Immunolocalization of proton-ATPase in the gills of the elasmobranch,Squalus acanthias

SUMMARY We have previously shown that continuous intravenous infusion of NaHCO3 for 24 h (∼1000 μmol kg-1 h-1)results in the relocation of V-H+-ATPase from the cytoplasm to the basolateral membrane in the gills of the Pacific dogfish. To further investigate this putative base-secretive process we performed similar experiments with the addition of colchicine, an inhibitor of cytoskeleton-dependent cellular trafficking processes. Blood pH and plasma total CO2 were significantly higher in the colchicines-treated,HCO3--infused fish compared with fish infused with HCO3- alone. The effect of colchicine was highest after 24 h of infusion (8.33±0.06 vs 8.02±0.03 pH units,15.72±3.29 vs 6.74±1.34 mmol CO2l-1, N=5). Immunohistochemistry and western blotting confirmed that colchicine blocked the transit of V-H+-ATPase to the basolateral membrane. Furthermore, western blotting analyses from whole gill and cell membrane samples suggest that the short-term (6 h) response to alkaline stress consists of relocation of V-H+-ATPases already present in the cell to the basolateral membrane, while in the longer term (24 h) there is both relocation of preexistent enzyme and upregulation in the synthesis of new units. Our results strongly suggest that cellular relocation of V-H+-ATPase is necessary for enhanced HCO3- secretion across the gills of the Pacific dogfish.

Section: Introductionsupporting

confidence: 90%

Microtubule-dependent relocation of branchial V-H+-ATPase to the basolateral membrane in the Pacific spiny dogfish (Squalus acanthias): a role in base secretion

Tresguerres

Parks

Katoh

et al. 2006

“…Control and AIF, H + -ATPase-positive cells showed a diffuse signal throughout the cytoplasm, slightly stronger in the apical region (Fig.·7A,B). This sub-cellular localization is similar to that previously described by Wilson et al (1997).…”

Section: Blood Parameterssupporting

confidence: 81%

“…These transporters would be localized in the same cells as the enzyme sodium-potassium ATPase (Na + /K + -ATPase) (see Claiborne et al, 2002). The second hypothesis is based on the description of H + -ATPase in the gills of Squalus acanthias by Wilson et al (1997). However, the relationship between this transporter and acid secretion are based only on the subapical localization, and an analogy to the α-secreting cells of the mammalian collecting duct, the frog skin and the turtle urinary bladder (Brown and Breton, 1996;Kirschner, 2004).…”

mentioning

confidence: 99%

Regulation of branchial V-H+-ATPase,Na+/K+-ATPase and NHE2 in response to acid and base infusions in the Pacific spiny dogfish (Squalus acanthias)

Tresguerres

Katoh

Fenton

et al. 2005

100

SUMMARY To study the mechanisms of branchial acid-base regulation, Pacific spiny dogfish were infused intravenously for 24 h with either HCl (495± 79μmol kg-1 h-1) or NaHCO3 (981±235μmol kg-1 h-1). Infusion of HCl produced a transient reduction in blood pH. Despite continued infusion of acid, pH returned to normal by 12 h. Infusion of NaHCO3 resulted in a new steady-state acid-base status at ∼0.3 pH units higher than the controls. Immunostained serial sections of gill revealed the presence of separate vacuolar proton ATPase (V-H+-ATPase)-rich or sodium-potassium ATPase(Na+/K+-ATPase)-rich cells in all fish examined. A minority of the cells also labeled positive for both transporters. Gill cell membranes prepared from NaHCO3-infused fish showed significant increases in both V-H+-ATPase abundance (300±81%) and activity. In addition, we found that V-H+-ATPase subcellular localization was mainly cytoplasmic in control and HCl-infused fish, while NaHCO3-infused fish demonstrated a distinctly basolateral staining pattern. Western analysis in gill membranes from HCl-infused fish also revealed increased abundance of Na+/H+ exchanger 2(213±5%) and Na+/K+-ATPase (315±88%)compared to the control.

“…The gills of elasmobranchs are most likely the site of HCO 3 -secretion (Hodler et al, 1955;Swenson and Maren, 1987), yet there has been little research concerning the potential molecular mechanisms responsible for Cl -/HCO 3 -exchange. The presence of VHA in elasmobranch gills has been known for some time (Wilson et al, 1997), and appears in cells separate to those with NKA (Piermarini and Evans, 2001;Claiborne et al, 2008), which is also consistent with results from the present study. In C. leucas, gill VHA staining was typically evident throughout the cell cytoplasm or confined to the basolateral membrane.…”

Section: Plasma Osmolality Urea and Electrolytesmentioning

confidence: 99%

Branchial osmoregulation in the euryhaline bull shark, Carcharhinus leucas: a molecular analysis of ion transporters

Reilly

Cramp

Wilson

et al. 2011

Self Cite

SUMMARYBull sharks, Carcharhinus leucas, are one of only a few species of elasmobranchs that live in both marine and freshwater environments. Osmoregulation in euryhaline elasmobranchs is achieved through the control and integration of various organs (kidney, rectal gland and liver) in response to changes in environmental salinity. However, little is known regarding the mechanisms of ion transport in the gills of euryhaline elasmobranchs and how they are affected by osmoregulatory challenges. This study was conducted to gain insight into the branchial ion and acid-base regulatory mechanisms of C. leucas by identifying putative ion transporters and determining whether their expression is influenced by environmental salinity. We hypothesised that expression levels of the Na