902 7. MERCURIALS 



It is interesting to inquire into how much Hg++ must be bound to the 

 erythrocytic membrane to cause hemolysis. The data of Meneghetti (1922) 

 indicate about 1.5 X 10' atoms/cell, but Jung (1947) believed this to be 

 too low and revised the figure on the basis of his results to 1.4 X 10^ atoms/ 

 cell. The data of Vincent and Blackburn (1958) allow a rough calculation 

 that K+ loss is induced by Hg++ at binding levels around 2 X 10' atoms/ 

 cell, although no hemolysis occurs, while maximal K+ loss and inhibition 

 of glucose uptake in human erythrocytes were found by Weed et al. (1962) 

 to be produced by 3.6-4.5 X 10^ atoms/cell. If there are 10 reactive SH 

 groups for each membrane protein of molecular weight 100,000, one can 

 estimate there to be around 3 X 10' SH groups per erythrocyte membrane. 

 However, although stromal SH groups have a greater affinity for Hg++, 

 hemoglobin SH groups account for around 85% of the total binding, so the 

 figures given above should be reduced if only membrane binding is desired. 

 All one can say is that the amount of Hg++ to alter membrane properties 

 is of the same order of magnitude as the estimated SH content of the mem- 

 brane. On the other hand, the number of molecules/ceU of the organic mer- 

 curials required for hemolysis is greater than necessary to cover the sur- 

 face of the sheep erythrocyte (Benesch and Benesch, 1954). For PM there 

 is a 4-fold excess and for mersalyl a 24-fold excess. Of course, the organic 

 mercurials probably do not lie flat on the membrane, but, more important, 

 it is not known how much of the mercurial is bound to hemoglobin or other 

 nonmembrane components. 



The kinetics of mercurial hemolysis are generally characterized by a lag 

 period, the duration of which is dependent on the mercurial concentration, 

 followed by a rather sudden hemolysis (Fig. 7-40). For sheep erythrocytes 

 there is a lag period of around 80 min when treated with 0.45 milf PM 

 (Benesch and Benesch, 1954), and for human erythrocytes the lag period 

 is 90 min at 37^ when exposed to 0.5 mM p-MB (Sheets et al, 1956 a). The 

 temperature is an important factor, since in the latter case the lag period 

 is around 200 min at 25°. The lag period is partly due to the slow binding 

 of these organic mercurials. Washing the erythrocytes 1 min after exposure 

 to p-MB protects completely, after 30 min protects partially, and after 

 60 min there is no protection (Sheets et al., 1956 a). On the other hand, 

 there is maximal uptake of Hg^"^ by erythrocytes within 5 min (Weed et 

 al., 1962). The osmotic fragility is altered after 3-min exposure to Hg++: 

 At 5.2 X 10'-5.5 X 10^ atoms/cell there is a decrease in the fragility, at 

 4.5 X 10^ atoms/cell there is an increased fragility and hemolysis. The ki- 

 netics for Hg++ and the organic mercurials appear to be quite different. The 

 very marked effects of PM concentration on the kinetics of hemolysis may 

 be seen in Fig. 7-40 for sheep erythrocytes, and a similar dependence has 

 been noted in rat erythrocytes (Moore, 1959). This might indicate a rather 

 critical level of membrane binding to produce hemolysis. The uptake of 



