178 • Alternatives to Animal Use in Research, Testing, and Education 
changes in membrane permeability, and damage 
to some part of the cell structure. Those functions 
having to do with viability and growth are most 
frequently measured because they require an in- 
tegration of many physiologic events within the 
cell, are sensitive, and lend themselves to automa- 
tion (73). 
Quantifiable tests are preferred over subjective 
ones, and a wide variety of quantitative approaches 
are available to measure irritation, including the 
release of prostaglandins (35); the production of 
enzymes (46), proteins (57), antigens, antibodies, 
or hormones (73); and the migration of certain 
white blood cells (macrophages) to the area of ir- 
ritation (12,101). Irritation can also be measured 
by the extent to which cells exfoliate from the sur- 
face of the tissue. The extent of damage can be 
determined by counting cells and by examining 
the nuclei (102). Another indicator of irritation, 
the integrity of cell membranes, can be monitored 
through the uptake of nutrients through the cell 
wall. Where the nutrient uptake is active (that is, 
when the cell is required to expend energy for 
transport), uptake can also be used to indicate 
changes in metabolism (86,102). 
Liver cells have been the subject of considerable 
research, in part because they play such an im- 
portant role in an organism’s removal of toxic sub- 
stances and in part because they retain most of 
their special functions when cultured. The re- 
sponse of liver cells to toxic substances may be 
measured in many ways: the use of sugar as an 
indication of metabolic activity; the production of 
proteins or other substances that have been cor- 
related with toxicity; uptake of amino acids as an 
indication of protein synthesis; changes in appear- 
ance that parallel those observed in livers of whole 
animals (106); and morphological changes and re- 
ductions in viability (75). Other promising tech- 
niques in this rapidly expanding field include cul- 
turing: 
• beating heart cells to detect the effect of cer- 
tain vapors on irregularities in heartbeat (68); 
• rabbit kidney tubules to detect substances that 
can cause acute renal failure, and rat vaginal 
tissue to test vaginal irritancy of contracep- 
tives (27); 
• various kinds of cells to test for biocompati- 
bility of implants (15,52,53); and 
• nerve cells to test for the synthesis of neuro- 
Dispensing Apparatus for Delivery of Culture Medium to Cells Within a Plastic Culture Plate 
Photo credit: The Johns Hopkins University 
