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A test being developed by scientists at the University of Paisley promises to help pharmaceutical firms avoid using animals to try new drugs for the treatment of angina, toxic poisoning and other diseases.

John McLean of the university's department of biological sciences and project leader says pharmaceutical firms want to reduce the level of animal experimentation for ethical and financial reasons.

Paisley scientists aim to exploit the fact that many diseases are associated with changes in the levels of hormones and chemicals in the body such as neurotransmitters. The molecules which make up these chemicals bind to specific receptors on the surface of cells. Drugs which block the activation of these areas can be used to restrict the influence of these molecules, so halting attack of the cell by the disease.

Dr McLean and his team are using genetic engineering to insert a gene into cultured human cells to produce a special enzyme which results in a colour change typically to blue or yellow. This change is noticeable by eye. The gene is switched on when special "signalling molecules" inside the cell are released because receptors have been activated, indicating that the cell is under attack. The gene functions as a "reporter" to indicate an attack has taken place. Dr McLean says: "What we are looking for, when testing new drugs, is no colour change, indicating that receptor sites have been blocked and attack repulsed."

With conditions such as angina and toxic shock, an important signalling molecule is cyclic GMP (cGMP) which helps control muscle tone and so determines blood pressure. The pharmaceutical industry is already using the reporter technique to screen for a related signalling molecule called cyclic AMP (cAMP).

Dr McLean says: "We want to use genetic engineering to manipulate the analysis for cAMP so that cGMP can be measured." He is confident his team can develop a reporter system that will dramatically slash the costs of testing new drugs. "It should make it possible to reduce the number of animals needed in the research."