Volume- and catecholamine-dependent regulation of Na/H antiporter and unidirectional potassium fluxes in Salmo trutta red blood cells |
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Authors: | S N Orlov E J Cragoe Jr O Hänninen |
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Institution: | (1) Laboratory of Physical Chemistry of Biomembranes, School of Biology, Moscow State University, Moscow, Russia;(2) 19446 Landsdale, Pennsylvania, USA;(3) Department of Physiology, University of Kuopio, P.O. Box 1627, SF-70211 Kuopio, Finland |
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Abstract: | β-Adrenergic- and volume-dependent regulation of 22Na influx and 86Rb influx and efflux in erythrocytes of brown trout (Salmo trutta m. lacustris) were studied. Norepinephrine (10-6 mol·1-1) increased the rate of 22Na influx 10-to 20-fold via the activation of a Na/H exchanger (ethyl isopropyl amiloride inhibited component of 22Na influx). Unlike carp erythrocytes the activity of the Na, K-pump (ouabain-inhibited 86Rb influx) was only slightly (25–35%) increased by norepinephrine. The norepinephrine-induced increment of Na, K-pump activity
was completely abolished by ethyl isopropyl amiloride thus indicating that this effect was mediated by Na/H exchanger-induced
increase of intracellular Na+ concentration. Cell shrinkage in hyperosmotic media resulted in a several-fold activation of the Na/H exchanger. Cell swelling
in hypotonic media increased both the rate of K, Cl-cotransport ((dihydroindenyl)oxy)alcanaic acidsensitive components of
86Rb influxe and efflux] and passive permeability (leakage) of erythrocyte membranes for Na+ and K+. No volume-dependent regulation of Na, K, 2Cl-cotransport (bumetanide-sensitive components of 86Rb fluxes) was found. It may be concluded that the regulation of monovalent cation transport in erythrocytes of fast-moving
(carnivorous) brown trout differs essentially from that in slowly moving (herbivorous) carp. |
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Keywords: | Na K-pump Na/H exchange Catecholamines Cell volume Fish erythrocytes |
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