MONDAY, May 14 (HealthDay News) -- An enzyme called Pak 1 acts on the heart's pacemaker cell in order to slow a racing heartbeat, according to a study by American and British scientists.

A single cell in the human heart -- the "pacemaker" cell -- controls heartbeat. The cell adjusts the heartbeat in order to increase or decrease blood flow to the body depending on activities such as exercise, eating, and sleeping.

In this study, researchers showed that the enzyme Pak 1, which is present at high concentrations in the heart, reduces the action of adrenaline and adrenaline-like chemicals on the pacemaker cell in order to put the brakes on rapid beating of the heart.

"The enzyme works through calcium and potassium channels that we know to be key players in the generation and regulation of pacemaker activity," first author Yunbo Ke, a research assistant professor of physiology and biophysics at the University of Illinois at Chicago (UIC), said in a prepared statement.

The study was published in the May 11 issue of the journal Circulation Research.

"Although adrenaline and other mechanisms that accelerate the heart rate have been well studied, mechanisms that might act as a brake are poorly understood," principal investigator R. John Solaro, distinguished university professor and director of the center for cardiovascular research and head of physiology and biophysics at UIC, said in a prepared statement.

"Identification of this previously unknown molecular mechanism for slowing the heartbeat may offer new avenues of diagnosis, drug design and treatment of many common heart diseases," Solaro said.

He noted that disturbances of pacemaker control are common in heart diseases and can result in fatal arrhythmias and stroke. Current treatment of arrhythmia involves destruction of tissue around a malfunctioning pacemaker cell and placement of a mechanical pacemaker.

Ke also noted that "now that we know something of how this enzyme works in the pacemaker cell, we may discover it is involved in the regulation of other processes, particularly in the brain, where it is also highly expressed."

More information

The U.S. National Heart, Lung, and Blood Institute has more about arrhythmia.