Scott K. Parks

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

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 CO2 l-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.

Signal transduction in multifactorial neuroendocrine control of gonadotropin secretion and synthesis in teleosts-studies on the goldfish model.

In teleosts, gonadotropin (GTH) secretion and synthesis is controlled by multiple neuroendocrine factors from the hypothalamus, pituitary and peripheral sources. Pituitary gonadotropes must be able to differentiate and integrate information from these regulators at the cellular and intracellular level. In this article, the intracellular signal transduction mechanisms mediating the actions of some of these regulators, including GTH-releasing hormones, pituitary adenylate cyclase-activating polypeptide, dopamine, ghrelin, sex steroids, activin, and follistatin from experiments with goldfish are reviewed and discussed in relation with recent findings. Information from other teleost models is briefly compared. Goldfish gonadotropes possess multiple pharmacologically distinct intracellular Ca2+ stores that together with voltage-sensitive Ca2+ channels, Na+/H+ exchangers, protein kinase C, arachidonic acid, NO, protein kinase A, ERK/MAPK, and Smads allows for integrated control by different neuroendocrine factors.

Chloride uptake and base secretion in freshwater fish: a transepithelial ion-transport metabolon?

Despite all the efforts and technological advances during the last few decades, the cellular mechanisms for branchial chloride uptake in freshwater (FW) fish are still unclear. Although a tight 1:1 link with \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Theoretical considerations underlying Na+ uptake mechanisms in freshwater fishes ☆

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Intracellular pH regulation in isolated trout gill mitochondrion-rich (MR) cell subtypes: Evidence for Na+/H+ activity

\end{document} secretion has been established, not much is known about the identity of the ion‐transporting proteins involved or the energizing steps that allow for the inward transport of Cl− against the concentration gradient. We propose a new model for Cl− uptake in FW fish whereby the combined action of an apical anion exchanger, cytoplasmic carbonic anhydrase, and basolateral V‐type H+‐ATPase creates a local [ \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Serotonin-induced high intracellular pH aids in alkali secretion in the anterior midgut of larval yellow fever mosquito Aedes aegypti L.

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