Editorial board editor-in-chief

Fig. 4.
 
Average erythrocyte life span in various animal species
Under these circumstances it is necessary to replace old red 
blood cells with the young ones. Hemolysis of erythrocytes must 
be and is in fact controlled. Intravascular hemolysis causing the 
release of hemoglobin in approximately 200 billion erythrocytes 
daily would overwhelm the compensatory mechanisms of the 
body. Therefore, this process is programmed and controlled, 
similar to apoptosis [12,15]. Only approximately 10% of red 
blood cells is destroyed intravascularly [11]. Red blood cells are 
devoid of a nucleus and mitochondria. For this reason there are 
no cellular organelles that are critical for apoptosis in the tradi-
tional sense. However, certain morpho-logical features such as 
cell shrinkage as a consequence of intracellular luid loss and 
characteristic blebbing of the plasma membrane can be found in 
erythrocytes. Analogically to apoptosis, increased concentrations 
of calcium ions have also been found in dying erythrocytes. This 
in turn activates calcium-dependent potassium channel (Gardos 
Cytoplasmic pH was found to be slightly lower in old blood 
cells than in the young ones [17]. However, reduction in enzy
-
matic activity in aging erythrocytes followed by reduced ability 
to synthesize ATP was not conirmed. It appears then that it 
is not the main reason for blood cell death [18,19]. Reduced 
activity of hexokinase, glucose-6-phosphate dehydrogenase and 
pyruvate kinase in reticulocytes persists only for several days 
after the appearance of erythrocytes in the circulation, however, 
it remains unchanged afterwards. The only exception is per
-
manent reduction in the activity of pyrimidine 5`-nucleotidase 
and AMP deaminase [11]. However, reduced activity of these 
enzymes may be a part of the blood cell program, because DNA 
is almost totally removed in the denucleation process, whereas 
RNA which is useless for the remaining stages of erythrocyte’s 
life undergoes enzymatic degradation. Especially CMP and 
UMP do not play any further metabolically important role in the 
erythrocyte, therefore they must be degraded to nucleosides 
which undergo diffusion [21].