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Wednesday, July 29, 1998 Published at 04:52 GMT 05:52 UK


Scientists crystalise ideas on kidney stones

Vital protein was detected in the urine

A protein previously only detected in white blood cells may play a key role in the prevention of kidney stones, according to researchers.

The discovery could lead to the development of effective treatments for the painful condition.

Researchers detected the protein, called calgranulin, in minute amounts in the kidney and in urine.

Powerful effect

They found that calgranulin has a powerful stunting effect on the growth of calcium oxalate crystals - the major component of kidney stones.

Dr Sokalingum Pillay, of the University of Chicago, also discovered that calgranulin, which is made up of two distinct sub-units, is often defective in people with kidney stones.

In kidney stone sufferers the two sub-units do not come together to form the active calgranulin protein.

Dr Pillay said: "Measuring calgranulin in urine could become a new diagnostic tool for determining if a patient is at high risk for forming kidney stones, and preventive measures could be taken."

Kidneys should be riddled

[ image: Chicago: Scene of the breakthrough]
Chicago: Scene of the breakthrough
According to the basic laws of chemistry, kidneys should be riddled with stones.

However, although the kidney is supersaturated with calcium and oxalate, the basic components of kidney stones, only 3-5% of people in the Western Hemisphere form them.

Most people pass microscopic calcium oxalate crystals with their urine before they can grow into dangerous masses.

Over the past ten years, several proteins have been found that have some effect on slowing or stopping crystal formation, but none with the potency of calgranulin, which is more than twenty times more potent than any other known crystal inhibitors.

Artifical solutions

Dr Fredic Coe, who also worked on the project, said: "Calgranulin exists in trace amounts. It's effective at preventing crystal formation at concentrations one million times lower than the urine concentration of calcium and one hundred thousand times lower that the urine concentration of oxalate."

The researchers created artificial solutions that mimicked the conditions inside the kidney, minus any crystal-prohibiting proteins, and calcium oxalate crystals began to aggregate. When they added minute amounts of purified calgranulin, crystal growth slowed down considerably.

It is thought calgranulin works by binding to the surface of the calcium oxalate crystal lattice where crystal growth takes place, thereby preventing the crystals from getting bigger or combining to form a large mass.

Calgranulin may also prevent crystals from adhering to renal tubules in the kidneys, a prerequisite for the formation of kidney stones.

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