Catecholamine- and volume-dependent ion fluxes in carp (Cyprinus carpio) red blood cells |
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Authors: | S N Orlov G A Skryabin |
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Institution: | (1) Laboratory of Physico-Chemistry of Biomembranes, School of Biology, Moscow State University, 119899 Moscow, Russia;(2) Present address: 3850, rue Saint-Urbain Pavillon Marie de la Ferre, H2W 1T8 Montreal, Quebec, Canada |
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Abstract: | In carp erythrocytes, noradrenaline (10-6 mol·l-1) induces a 30- to 40-fold activation of Na+/H+ exchange (the ethylisopropylamiloride-inhibited component of the 22Na influx) and a fourfold stimulation of the Na+, K+ pump (ouabain-inhibited component of 86Rb influx). In both cases the effect of noradrenaline is blocked by propranolol but not phentolamine and is imitated by forskolin. An activator of protein kinase C (-phorbol 12-myristate, 13-acetate) increases Na+/H+ exchange by 10 times and decreases the Na+, K+ pump activity by 20–30 percent. In the presence of ethylisopropylamiloride the increment of the Na+, K+ pump activity induced by noradrenaline is reduced by 35–45 percent, indicating the existence of a Na+/H+ exchange-independent mechanism of the Na+, K+ pump regulation by -adrenergic catecholamines. Hypertonic shrinkage of carp erythrocytes results in a 40- to 80-fold activation of Na+/H+ exchange, whereas hypotonic swelling induces an increase in the rate of 86Rb+ efflux which is inhibited by furosemide by about 30–40 percent. The rate of pH0 recovery in response to acidification or alkalinization in rat erythrocytes is approximately 15 times as fast as in carp erythrocytes. Unlike in rat erythrocytes, valinomycin does not cause an alkalinization of incubation medium in carp erythrocytes indicating the absence of conductive pathway in the operation of anion transporter protein. A scheme is suggested which describes the interrelation of Na+/H+ exchange, Na+, K+ pump and a non-identified system providing for K+ efflux in cell swelling, regulation of cell volume and cytoplasmic pH in fish erythrocytes under conditions of deep hypoxia and high activity.Abbreviations cAMP
cyclic adenosine monophosphate
- CCCP
carbonylcyamide m-chlorophenylhydrazone
- DMSO
dimethylsulphoxide
- EIPA
ethylisopropylamiloride
- NA
noradrenaline
- PMA
-phorbol 12-myristate, 13-acetate
- RVD
regulatory volume decrease
- RVI
regulatory volume increase |
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Keywords: | Na+ K+-pump Na+/H+-exchange Anion transport Erythrocytes Carp Cyprinus carpio |
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