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Thursday, 18 May, 2000, 11:15 GMT 12:15 UK (BBC)

Tarantula 'may save lives'

A poisonous tarantula spider may help save the lives of people suffering heart attacks and brain tumours.

A chemical in the Chile Rose's venom has been found to block a basic mechanism in cells important to a wide range of biological functions.

The Chile Rose was a good choice because it is a big spider that produces large amounts of venom.

It is the latest example of the benefits that creatures commonly thought of as killers can have in the treatment of humans.

Researchers at the University of Buffalo in New York State, US, found that part of the venom blocked the action of pores in the membrane around cells through which electrically charged particles travel.

The pores, called "stretch-activated channels" - because stretching the cell membrane causes them to open and close - are known to initiate an abnormal form of rapid heart muscle contraction after a heart attack called ventricular fibrillation, which often proves fatal.

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Chief researcher Professor Frederick Sachs, said in the Journal of General Physiology: "If we can block the stretch-activated channels, we may be able to block fibrillation, a major cause of death following heart attacks."

Another possible area of treatment is brain tumours. Cancer invasion of brain tissue causes surrounding normal cells to release chemicals believed to facilitate or accelerate tumour growth.

Stretch-activated channels are thought to provide the signal for normal cells to produce the growth-factor chemicals.

The researchers discovered the affect of the spider's venom after a series of tests on poisonous arachnids.

"Basically we went on a fishing expedition, screening things we thought might work," the Professor said.

"Eventually we started looking at the venom of poisonous arachnids.

"We didn't know why any bug would possibly make such a thing, but thought it was worth a try."

Tests on scorpion venoms, known to affect nerve impulses, drew a blank.

But spiders, whose venom is kept in laboratories for research purposes, proved more hopeful.

Professor Sachs said: "The Chile Rose was a good choice because it is a big spider that produces large amounts of venom."

The raw venom was separated into between 100 and 150 components to identify the most active substance.

This turned out to be a peptide, a protein building block, labelled GsMTx-4, after the spider's Latin name Grammostola spatulata.

Next, to rule out the possibility of contaminants, the researchers genetically modified a strain of bacteria to produce a pure form of the same peptide.

Both the artificially produced peptide and the one obtained directly from the spider blocked the stretch-activated channels.

Professor Sachs said the result opened the door to studies requiring large amounts of peptide that would assist in the design of new drugs.

It also facilitated studies that would look at the effect of the peptide on many cells at once, or on whole organs and tissues.