The regulation of cellular volume in renal cortical slices incubated in hyposmotic medium.

Abstract

SUMMARY1. Changes in water and ion contents of renal cortical slices from rat, rabbit and guinea-pig incubated in medium of a half normal osmolarity were followed over 60 min incubation at 25°C.2. Metabolizing slices gained water and lost sodium and chloride but not potassium. These changes reflected in part changes in cellular composition, and were complete within 5 min. A new steady-state was then maintained for a further 55 min.3. Slices initially incubated for 60 min with ouabain, also lost sodium and chloride when transferred to the hyposmotic medium but did not, in the first minutes, lose any further potassium. Ouabain, in concentrations sufficient to produce maximal inhibition of the Na-K ATPase, did not cause additional cellular swelling in the hyposmotic medium. 4. The results offer no support for the claim that cellular volume in metabolizing renal cortical cells exposed to hyposmotic media is regulated by loss of cellular potassium. They suggest that under such conditions the regulation of volume involves the same ouabsin-insensitive mechanism as is seen in cells incubated in isosmotic medium.

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

“…These results are similar to those obtained by Kregenow (1971a) in duck erythrocytes, who also showed a significant drop in red cell K concentration. Hughes and MacKnight (1976) showed no change in cell K content at 25°, but, on recalculating their data, we found that a drop in cell concentration of K was also evident. The differences between theirs and the present experiments may be due to the different temperatures and the presence of bicarbonate in ours.…”

“…In hypotonic solutions, renal tubular cells swell and then, in time, return incompletely to their original volume (Dellasega and Grantham, 1973;Hughes and MacKnight, 1976;Gyory, Kweifio-Okai and Ng, 1981). 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).…”

“…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).…”

“…In hypotonic solutions some have found that Na was extruded from renal cortical cells, K remaining constant (Hughes and MacKnight, 1976), whereas others have found that mainly K was extruded (Kregenow, 1971b). The experiments of Hughes and MacKnight (1976) may not be directly applicable to phenomena of kidney transport, since they were performed at 25° and because their solution lacked bicarbonate ion, shown to play a significant role in renal cellular Na transport (Fromter, Rumrich and Ullrich, 1973).…”

“…In hypotonic solutions some have found that Na was extruded from renal cortical cells, K remaining constant (Hughes and MacKnight, 1976), whereas others have found that mainly K was extruded (Kregenow, 1971b). The experiments of Hughes and MacKnight (1976) may not be directly applicable to phenomena of kidney transport, since they were performed at 25° and because their solution lacked bicarbonate ion, shown to play a significant role in renal cellular Na transport (Fromter, Rumrich and Ullrich, 1973). There are no data in the literature on cellular content or concentration of Na, K or Cl in response to hypertonic saline and non-electrolyte solutions at 37° in kidney cortical cells, although Kleinzeller, Nedvidkova and Knotkova (1967) reported changes at 25° but with only low Na and mannitol.…”