Effect of cell ageing on Ca2+ influx into human red cells.
The effect of cell ageing on Ca2+ entry was studied in this work, using sub-populations of young and old human red cells, separated by stringent percoll density gradients. Additionally, the influence of an osmotic gradient was investigated as a model for shear stress. Ca2+ entry was assessed at 37 degrees C, under conditions where the Ca2+ pump was either inhibited by NaVO3 (0.5-10 mM) or inactivated by ATP depletion. The entry was linear with time up to 1 h. No differences in Ca2+ influx between the two sub-populations were detected in isotonic Na(+)-medium. In contrast, after incubation in anisosmotic media, Ca2+ entry into old cells was significantly higher than into younger cells. In hypotonic Na(+)-medium, the entry into old cells was not affected by La3+ (10 microM) whilst it was partially blocked by Gd3+ at a similar level (half-maximal effect attained with about 1 microM Gd3+). The entry into young cells was only slightly stimulated by these lanthanides at low concentrations (10 microM), regardless of the tonicity of incubation medium. Further increasing Gd3+ levels above 10 microM markedly enhanced Ca2+ entry into both cell types. The selective blockade of Ca2+ influx by low Gd3+ concentrations suggests presence of mechano-sensitive channels, that become preferentially activated in old cells. Activation of these channels during in-vivo microcirculation may help to explain the increased Ca2+ content of senescent cells.
Romero
P J
PJ
Laboratory of Membrane Physiology, Faculty of Sciences, Central University of Venezuela, Caracas. romepe@mixmail.com
Romero
E A
EA
D000255:Adenosine Triphosphate / Q000502:physiology; D002118:Calcium / Q000097:blood*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D016922:Cellular Senescence / Q000187:drug effects / Q000502:physiology*; D004912:Erythrocytes / Q000145:classification / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology*; D006493:Heparin / Q000494:pharmacology; D006801:Humans; D008674:Metals, Rare Earth / Q000494:pharmacology; D009355:Neomycin / Q000494:pharmacology; D009996:Osmotic Fragility / Q000187:drug effects
D002121:Calcium Channel Blockers; D008674:Metals, Rare Earth; D000255:Adenosine Triphosphate; D006493:Heparin; D009355:Neomycin; D002118:Calcium