title: Progressive inhibition of the Ca pump and Ca:Ca exchange in sickle red cells.
abstract: Sickle cell anaemia red cells (SS) were reported to have a high Ca content and an increased Ca uptake on deoxygenation, but their Ca-pump activity was described as normal. This seemed puzzling because the saturated Ca-extrusion rate of the normal, high Ca-affinity Ca pump is about 10 mmol per 1 cells per h (refs 3, 4) and the highest sickling-induced Ca influx reported in SS cells and observed in ATP-depleted sickle-trait (SA) red cells never exceeded 0.2 mmol per 1 cells per h. Normal pump performance is, therefore, incompatible with Ca accumulation unless SS cells have abnormally high Ca-binding capacity. We provide here evidence which suggests that SS cells have normal Ca-buffering capacity and probably genetically normal Ca pumps, but that the sickling process causes progressive Ca-pump failure and a marked reduction in Ca:Ca exchange.
mesh_terms: D000755:Anemia, Sickle Cell / Q000097:blood*; D001692:Biological Transport / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000097:blood*; D000252:Calcium-Transporting ATPases / Q000097:blood; D004913:Erythrocytes, Abnormal / Q000378:metabolism*; D006801:Humans
chemical_list: D000001:Calcimycin; D000252:Calcium-Transporting ATPases; D002118:Calcium