Utrecht
THOUSANDS of rabbits could be saved from distressing experiments if dead
chickens were used in their place, a conference in Utrecht was told last
week.
Rabbits are widely used to establish whether chemicals, such as those used in
cosmetics, are hazardous to humans. In the Draize test, prescribed by the
European Commission, chemicals are dripped into rabbits鈥� eyes. The redness of
their eyelids and opacity of their corneas are then taken as a measure of the
damage the chemicals can cause. But Menk Prinsen of the Dutch research
organisation TNO in Zeist says that equally accurate results can be obtained
using the eyes of butchered chickens from slaughterhouses.
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Prinsen says he can measure the potency of a chemical from its effect on the
thickness of a chicken鈥檚 cornea. The cornea remains active for several hours
after death, so the results are as accurate as those from the eyes of living
animals, he says.
An irritating substance will leave holes in the thin surface membrane of the
cornea. Water applied to the surface can then reach the spongy stroma inside the
cornea, causing it to swell. Intact, a chicken鈥檚 cornea is slightly thicker than
half a millimetre; when damaged, it can swell by up to 60 per cent.
鈥淗is method has great potential,鈥� says Michael Balls, head of the European
Centre for Validation of Alternative Methods in Ispra, Italy. 鈥淏ut there鈥檚 a
great deal of difficulty with replacing the rabbit eye test.鈥�
Britain鈥檚 Home Office and the European Commission tested Prinsen鈥檚 method two
years ago, along with other alternatives. These included tests with cows鈥� eyes
and blood vessels from chicken embryos. But none could reliably reproduce the
results of the rabbit eye test. The reason, says Balls, is that 鈥渢he data from
rabbit tests themselves are so variable they can鈥檛 be reproduced鈥�.
Prinsen argues that this is because the redness, swelling and opacity of
rabbits鈥� eyes are estimated subjectively, and what one researcher calls 鈥渓ight鈥�
redness, another calls 鈥渉eavy鈥�. 鈥淪ince no test can duplicate this, European
regulators and industry stick to the old ways.鈥�
Prinsen thinks his test, or something similar, could at least be used to
separate out the totally innocent or very dangerous chemicals from more
borderline cases. This would cut the number of live rabbits used in tests.
Balls understands Prinsen鈥檚 frustration: 鈥淭here鈥檚 conservatism with the
regulators as well as industry. But there鈥檚 willingness in both camps too.鈥� The
European Commission plans to ban the Draize test in the cosmetics industry from
1998 if there is an alternative available that satisfies everyone.