Localization and Role of Calcium in the Erythrocyte Coat: Effects of Enzymes and Storage

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Abstract
The effects of various treatments on [human] erythrocyte shape, surface, cell coat and Ca binding sites were investigated by high voltage electron microscopy (HVM), scanning electron microscopy (SEM) and conventional electron microscopy (TEM). Papain caused the formation of small blisters within the cellular surface as well as crenation and budding of the erythrocytes. After neuraminidase treatment, long filaments were observed to radiate from the surface of the erythrocyte. The other enzymes investigated, RNAse, DNAse, phospholipase, protease and trypsin, produced no demonstrable effect on the cellular structure, nor (with the possible exception of trypsin) on the cell coat as seen by subsequent staining with ruthenium red. Putative Ca binding sites on and in the erythrocyte membrane were demonstrated. Following incubation with radioactive Ca, activity was found in the erythrocyte membranes. Ca binding could be reduced by prior treatment of the erythrocyte with EDTA, neuraminidase, and to a lesser extent, by papain and trypsin. Other enzymes had no demonstrable effect. Stored erythrocytes showed a progressive diminution in Ca binding over 4 wk.
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