Boffins decipher how brakes are applied on a racing heartbeat

A new study has found how an enzyme Pak 1, acts on the hearts pacemaker to slow the rapid beating of the hearts fight-or-flight reaction to adrenaline.

Washington, May 12 : A new study has found how an enzyme Pak 1, acts on the heart's pacemaker to slow the rapid beating of the heart's 'fight-or-flight' reaction to adrenaline.

A single cell in the upper right chamber of the heart is responsible for setting the pace of the beating heart, triggering its neighbour cells to beat. In the human heart, one cell, that is the pacemaker cell beats faster or slower to induce a rhythmic heartbeat that varies to increase or decrease the blood flow to the body as we eat, sleep or exercise.

The study was conducted by a team of researchers including R. John Solaro and Yunbo Ke, at University of Illinois, Chicago in collaboration with colleagues in England at Oxford and Manchester.

"Disturbances of pacemaker control are common in heart diseases. When the heartbeat becomes non-rhythmic and chaotic, it can result in fatal arrhythmias and stroke," Solaro said.

Current treatment of arrhythmia requires destruction of tissue surrounding a chaotic pacemaker, followed by insertion of a mechanical pacemaker that can regulate the heartbeat.

As part of the study, researchers worked on characterizing and isolating the pacemaker cell.

They demonstrated that an enzyme called Pak 1, present in high concentrations in the heart, signals depression in the action of adrenaline and adrenaline-like chemicals on the pacemaker cell, playing an important role in slowing down the heart rate.

"The enzyme works through calcium and potassium channels that we know to be key players in the generation and regulation of the pacemaker activity," Ke said.

"Although adrenaline and other mechanisms that accelerate the heart rate have been well studied, mechanisms that might act as a brake are poorly understood," Solaro said.

"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 added.

"Further, 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," Ke added.

The findings of the study were published in the May issue of Circulation Research.

ANI