906 7. MERCURIALS 



Collier (1960). However, Hg++ and p-MB can produce hemolysis without 

 significant loss of glutathione, whereas iodoacetate and iV-ethylmaleimide 

 reduce the glutathione completely without lysis. Jacob and Jandl (1962) 

 also showed that p-M3 reacts readily with glutathione in solution, but does 

 not attack erythrocyte glutathione, and concluded that p-MB does not 

 penetrate into the cells. However, Weed et at. (1962) found that of the three 

 major sources of SH groups in the erythrocyte — stroma, hemoglobin, and 

 glutathione — the last has the lowest affinity for the mercurial and consti- 

 tutes only 5% of the total SH groups. It is thus possible that glutathione 

 would be reacted only when aU the other SH groups are saturated. In any 

 event, it is evident that glutathione does not play a significant role in 

 hemolysis. 



Hg++ is able to produce structural changes in the erythrocytic membrane 

 which are detectable by electron microscopy (Jung, 1947). Isolated hemo- 

 globin-free membranes treated with high concentrations of Hg++ (37 ulM) 

 show gross changes in structure — a crumpling with increased density and 

 apparent thickness — but with lower concentrations (0.37 vaM) the pic- 

 ture is different, a network of holes appearing in the otherwise unaltered 

 membrane. Intact erythrocytes treated with 1.85 ruM Hg++ for several 

 hours no longer lyse in distilled water, and the membrane is seen to have 

 been replaced by a thick mass of coagulated protein. Certain changes in 

 the over-all erythrocyte configuration were also observed by Vincent (1958) 

 in preparations allowed to bind Hg++ for 5 min, especially sphering and 

 crenation. Possibly a more detailed study of structural changes induced by 

 low prohemolytic concentrations of the mercurials would be useful in clari- 

 fying the mechanism of hemolysis. 



We have assumed with others in this discussion of hemolysis and permea- 

 bility changes brought about by the mercurials that SH groups only are 

 attacked. Certain nonelectrolytes, such as glucose and glycerol, enter the 

 erythrocyte by facilitated diffusion and, since the transport is usually ef- 

 fectively blocked by SH reagents, it has been thought that SH groups are 

 involved in some manner. We have seen that Wilbrandt (1941) claimed a 

 marked -reduction in glycerol permeability with 0.05 vaM Hg++. Further- 

 more, it was believed that inhibition of glycerol penetration occurs only 

 while the Hg++ is entering the cells, i.e., when the Hg++ is bound to the 

 membrane. When the Hg++ has been picked up by the hemoglobin, there 

 may be little left in the membrane and the permeability to glycerol is re- 

 stored. LeFevre (1948) established that p-MB likewise blocks glycerol entry 

 into the human erythrocyte. However, Barnard and Stein (1958) have sug- 

 gested that an imidazole group is involved in this transport. The fact that 

 histidine as well as cysteine can reverse the inhibition (it requires a 5- to 

 10-fold excess of histidine) is not valid evidence; it simply shows that mer- 

 curials are bound to histidine. It was also claimed that mercurial action 



