New research into muscle contraction will give scientists a better understanding of bladder problems and pain during childbirth

Aug 1 2005

Professor Susan Wray, who heads the UK's top rated Department of Physiology, and Dr. Ted Burdyga, are studying muscles in the wall of the ureter, which connects the kidney to the bladder, to understand how muscles respond to signals in the body telling them to contract or relax.

Their research, supported by the Medical Research Council, is published in this week's issue of Nature.

Muscles contract and relax to allow the body to perform crucial activity. Electrical signals tell the muscle when to contract, but when the muscle needs to relax, the signal is deliberately ignored. Until now scientists have been unable to understand how the body ignores this signal.

The team found that calcium, which allows muscle contraction to take place, enters the body's cells in response to electrical signals. The calcium fills up a small structure in the cell and when this is full and starts to empty, it forces the muscle to relax by preventing any more calcium entering the cell, even when it receives contraction signals.

Professor Wray explains: "Electrical signals in nerves and muscles are important for all activity, from thinking to drinking. It is important for the body to be active, but it is also important for it to relax, so that it doesn't over work itself. For example, in childbirth the uterus contracts and relaxes at regular intervals to allow a baby to pass through the birth canal.

"But when we get cramps for example, our muscle is contracting too hard or too often and in the case of the ureter it would cause kidney damage. It is therefore crucial that our muscles have periods of relaxation and we have now uncovered how this occurs. This understanding should allow doctors to work more accurately with the body's natural mechanisms when treating patients."