Changes in the Ca2+-Transport Processes of Red Cells during Cold Storage in ACD

Authors


Dr I. Szász, National Institute of Haematology and Blood Transfusion, 1113 Budapest, Daróczi ut 24, Hungary.

Abstract

In order to characterize Ca2+-transport in red cells stored in ACD Ca2+-loading and Mg2+-depletion by the ionophore A23187, CaATPase activity determination in intact cells and an accurate Ca2+-influx technique were adapted to preserved blood. Active Ca2+-efflux (pump) was measured in rejuvenated cells loaded by Ca2+ with A23187. The rate of Ca2+-pump declined only slightly during 3 weeks of storage (from 80 ± 15 to 66 ± 17 μmoles Ca2+/l. cells/min) and a marginal trend of decrease in the Ca:ATP ratio was observed (from 1.96 ± 0.15 to 1.88±0.11). Passive Ca2+-influx (leak) was studied in regenerated cells in which the Ca2+-pump was blocked with 0.2 mm lanthanum. Ca2+-influx showed a slow increase during the first 3 weeks of storage (from 0.4±0.16 to 1.25±0.4 μmoles Ca2+/l. cells/min), later it increased rapidly. Passive Ca2+ leak and exchange transport were studied in unregenerated, phosphate ester-depleted cells. In this case passive Ca2+-influx increased 2–3-fold as early as 1–2 d after storage in ACD. This initial increase was followed by a continuous slow enhancement that reached a flux of 3.5±0.7 μmoles Ca2+/l. cells/min after 3 weeks of storage. The passive Ca2+-permeability increase that occurred during storage could be readily compensated by the Ca2+-pump without causing metabolic imbalance. The Ca2+-transport, of unregenerated stored cells, however, showed impairment under certain conditions (A23187+EDTA and lanthanum treatments, ghost preparation). The Ca2+-induced shape changes were reversible and ran parallel with the cell Ca2+ level during Ca2+-pumping up to 5 weeks of storage. This finding indicates a direct relationship between cell Ca2+ and shape.

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