Chapter I 

 WATER AND ELECTROLYTES 



I 



t is well known that when mammalian cells and tissue slices are 

 exposed to an unfavourable environment in an isotonic medium 

 in vitro the cells suffer an increase in volume and in weight. It is 

 also known that the increase in weight is due to accumulation of 

 water within the cell. Equally commonplace is the swelling of cells 

 in vivo demonstrable by standard histological methods which also 

 disclose vacuolation and haziness of the cytoplasm of the swollen 

 cells. These in vivo phenomena, seen in sections of fixed tissues, 

 notably liver, are known as cloudy swelling or hydropic change and 

 represent an early and often reversible indication of cellular injury 

 due to a large variety of damaging stimuli. Mitochondria isolated 

 from cells in this condition have been found, like the cells them- 

 selves, to be swollen and laden with water. It has been suggested 

 that some of the vacuolation seen in the cell cytoplasm in cloudy 

 swelling in fact represents such swollen mitochondria. 



It is established then that an early sign of cellular damage is an 

 influx of water into the cell. This is almost invariably accompanied 

 by another change, namely an outflow of potassium from cells. The 

 concentration of this ion within the cell is of course normally many 

 times greater than that in the extracellular fluid. Isolated mito- 

 chondria, too, lose potassium when they suffer damage. 



These phenomena, particularly the influx of water, have been 

 the starting point of many investigations into the water and electro- 

 lyte metabolism of cells. It is known from isotope studies that the 

 normal cell is freely permeable to water so the flow of water into 

 injured cells cannot be due to increased permeability to water. 

 Sabbatani (1901) showed that the swelling and water uptake of 

 tissues incubated in vitro in isotonic saline could be prevented by 

 rendering the surrounding medium hypertonic, a finding con- 

 firmed on innumerable occasions since. This observation led to the 



