MITOCHONDRIA, CELLS. AND TISSUES 



589 



a steady level of around 30%. Using different concentrations of Hg++, it 

 was shown that glucose uptake was about 10 times more sensitive to Hg^"^ 

 than was the respiration. However, the respiration of homogenates of dia- 

 phragm was inhibited fairly rapidly, there being no lag period and a maximal 

 effect occurred within 20 min. The lag period and the slow rate of respiratory 

 inhibition would thus indicate a delay in the penetration into the cells. The 



100 

 801- 

 60 

 40 

 20 

 INKO 



30 60 90 120 150 180 210 

 TIME (MIN) ^ 



100 



GLUCOSE UPTAKE 



"1 r 



I r 



RESPIRATION 



CuCl-,= l 



;mM 



30 60 90 120 150 180 210 240 270 300 

 TIME (MIN) *- 



Fig. 12-31. Inhibition of the ghicose uptake and the respiration of rat 

 diaphragm by HgClg and CuC'lj. (From Demis and Rothstein, 1955.) 



uptake of glucose probably involves reactions occurring at the surface of 

 the cells and thiLS is inhibited more readily than the respiration. Confir- 

 mation for this was obtained l)y histochemical localization of Hg++ after 

 exposure of the tissue for varying periods of time. There was a tendency 

 for the metal to be concentrated initially at the cell boundaries with pene- 

 tration into the cells occurring later, the rates of these processes correspond- 

 ing well to the inhibitions of glucose uptake and res])iration. The uptake 

 of Hg-^o^ by diaphragm was then determined and found to obey first-order 

 kinetics for tlie first 20 to 30 min. Tlie final concentration of Hg+"^ in the 



