Ouabain-insensitive salt and water movements in duck red cells. I. Kinetics of cation transport under hypertonic conditions.

Abstract

Duck red cells in hypertonic media experience rapid osmotic shrinkage followed by gradual reswelling back toward their original volume. This uptake of salt and water is self limiting and demands a specific ionic composition of the external solution. Although ouabain (10(-4)M) alters the pattern of cation accumulation from predominantly potassium to sodium, it does not affect the rate of the reaction, or the total amount of salt or water taken up. To study the response without the complications of active Na-K transport, ouabain was added to most incubations. All water accumulated by the cells can be accounted for by net salt uptake. Specific external cation requirements for reswelling include: sufficient sodium (more than 23 mM), and elevated potassium (more than 7 mM). In the absence of external potassium cells lose potassium without gaining sodium and continue to shrink instead of reswelling. Adding rubidium to the potassium- free solution promotes an even greater loss of cell potassium, yet causes swelling due to a net uptake of sodium and rubidium followed by chloride. The diuretic furosemide (10(-3)M) inhibits net sodium uptake which depends on potassium (or rubidium), as well as inhibits net sodium uptake which depends on sodium. As a result, cell volume is stabilized in the presence of this drug by inhibition of shrinkage, at low, and of swelling at high external potassium. The response has a high apparent energy of activation (15-20 kcal/mol). We propose that net salt and water movements in hypertonic solutions containing ouabain are mediated by direct coupling or cis-interaction, between sodium and potassium so that the uphill movement of one is driven by the downhill movement of the other in the same direction.

Ouabain-insensitive salt and water movements in duck red cells. III. The role of chloride in the volume response.

“…We have shown that cells incubated with ouabain in the absence of norepinephrine or hypertonicity maintain relatively stable volume by a simple exchange of internal potassium for incoming sodium (Schmidt and McManus, 1977a). The addition of furosemide to catecholamine-stimulated or hypertonically activated cells resuits in a stabilization of cell volume by a similar mechanism (Schmidt and McManus, 1977a, b).…”

“…When ceils were added to hypertonic solutions, the initial samples were taken as rapidly as possible (see Schmidt and McManus, 1977a). Both hypertonic and isotonic incubation solutions always contained (mM): ouabain, 0.1; glucose, 10; inorganic phosphate, 2.0-5.0; magnesium, 1.0.…”

“…W h e n sucrose was used as an osmotic r e p l a c e m e n t for [C1]o identical results w e r e o b t a i n e d . Mg-TES was titrated to the desired pH as described previously (Schmidt and McManus, 1977a). Na and K salts of gluconic acid isosmotically replaced NaC1 and KCI so that [Clio plus gluconate = 165 mM.…”

EFFECT OF HYPO‐ AND HYPERTONIC SALINE AND RAFFINOSE ON CELL CONTENT OF Na, Cl and K IN RESPIRING RAT KIDNEY CORTEX AT 37°

“…There was marked variation in tissue Na concentrations between different animal groups, ranging from 44 (Table la) to 102 (Table Ic) + For experiments with pericellular osmolality from 299 to 385 mosmol/kg IW (constant Na, n = 88). (Schmidt and McManus, 1977) and underscores the necessity for paired experiments. Similar variation between batches of tissue slices for Cl can be noted but less so for K. These control values lie well within the reported ranges for kidney tissue of rat or rabbit (Hughes and MacKnight, 1976;Law, 1975;Povedin and Boumedil-Povedin, 1972) and are amongst the lowest for Na and the highest for K reported even at 25°, indicating that there was no difficulty in maintaining oxygenation of these slices at 37°.…”

“…This tendency to restore original cell volume is referred to as volume regulation and is incomplete in renal epithelial cells but nearly complete in red cells (Kregenow, 1971a;Schmidt and McManus, 1977). The mechanism for this partial return to original cell volume in kidney cells has been variously attributed to a cation pump, either sensitive to inhibition of the Na"*"-, K+-ATPase by cardiac glycosides (Whittam and Willis, 1963) or not (Kleinzeller and Knotkova, 1964;Hughes and MacKnight, 1976), in which case a second cardiac glycoside-insensitive pump has been postulated (Schmidt and McManus, 1977). It has also been attributed to physical elastic 'recoil' forces of the cell (Kleinzeller and Knotkova, 1964) or its basement membrane (Linshav/ et al, 1977).…”