CA2+ TRANSPORT IN HUMAN ERYTHROCYTES AND NEUTROPHILS HYPOTONIC AND HYPERTONIC MEDIA

Neutrophiles and erythrocytes from fresh human blood were used to dete rmine the influence of medium osmolarity on the rate of Ca-45 accumula tion in the cells. The rate of Ca-45 uptake in neutrophiles increased by 20-50% in hypotonic media (200-100 mosM), while under hypertonic co nditions it increased by 30% at 420 mosM and was reduced to the initia l values at 520 mosM. The influx of Ca-45 in red blood cells was const ant under hypotonic conditions ana increased by 30% under hypertonic c onditions when the cells were incubated with 4 mM Na3VO4. The rate of Ca-45 influx in neutrophiles in the presence of 4 mM Na3VO4 was increa sed by more then an order of magnitude in both hypotonic and hypertoni c media. The data suggest that deviations of medium osmolarity from is otonic conditions sharply increase of the passive membrane permeabilit y for Ca2+ in neutrophiles, while there is only a slight increase in C a-45 influx in erythrocytes in hypertonic incubation media.