16 The Chemistry of the Injured Cell 



Metastatic Calcification 



In this condition, essentially normal tissues, particularly kidney 

 tubules, lung alveoli, thyroid and gastric mucosa, become the site 

 of calcium phosphate precipitation. The lesions are due to ab- 

 normal concentrations of calcium and phosphate in the blood. 



The cause of the abnormal blood levels may be over-activity of 

 the parathyroid gland or more rarely hypoparathyroidism, excessive 

 doses of vitamin D or destructive lesions of bone, e.g. secondary car- 

 cinoma. Other causes also exist. The essential feature of this type of 

 calcification is loss of calcium from the bones and its deposition 

 elsewhere. Much recent work has been performed on this subject 

 and it will not be pursued further here. 



Intracellular Accumulation of Calcium 



This phenomenon is known to occur as part of the disturbance 

 of electrolyte movements seen in cells and tissue slices in an un- 

 favourable environment in vitro. In addition, at least two types of 

 liver damage, due to carbon tetrachloride and thioacetamide show 

 in vivo intracellular calcium accumulation. This feature of cell in- 

 jury appears to be related to abnormal cell permeability, the calcium 

 possibly entering to maintain electrical neutrality in the face of 

 potassium loss, although the situation may be in fact more complex. 

 The massive entry of calcium may be particularly important in view 

 of the toxic effect of high concentrations of this ion on respiratory 

 enzyme systems. The calcium influx may thus be both a result and 

 a further cause of cellular injury. 



REFERENCES 



Appleboom, J. W. (1957) : Fed. Proc, 16:278. 



Conway, E. J. (1955) : Intern. Rev. Cytol., 4:377. 



Conway, E. J. and McCormack, J. I. (1953) : /. Physiol., 120:1. 



Harris, E. J. (1957) : /. gen. Physiol., 41:169. 



Judah, J. D. (1960) : Exp. Cell Res., iP:404. 



Leaf, A. (1956) : Biochem. J., 62:241. 



Leaf, A. (1959) : Ann. N. Y. Acad. Sci., 72:396. 



McLean, A. (1960) : Nature, 755:936. 



