Female, male hearts respond differently to stress hormone

According to a recent study published in Science Advances, male and female hearts react differently to the stress hormone noradrenaline. The mouse study might have implications for human cardiac problems such as arrhythmias and heart failure, as well as how different sexes react to different medications.

The researchers created a novel form of fluorescence imaging device that allows them to examine how a mouse heart responds to hormones and neurotransmitters in real time using light. Noradrenaline, commonly known as norepinephrine, was given to the mice. Noradrenaline is a neurotransmitter and a hormone that is involved in the body’s “fight or flight” response.

The results reveal that male and female mouse hearts respond uniformly at first after exposure to noradrenaline. However, some areas of the female heart return to normal more quickly than the male heart, which produces differences in the heart’s electrical activity.

“The differences in electrical activity that we observed are called repolarization in the female hearts. Repolarization refers to how the heart resets between each heartbeat and is closely linked to some types of arrhythmias,” said Jessica L. Caldwell, first author of the study. Caldwell is a postdoctoral scholar in the UC Davis School of Medicine Department of Pharmacology.

“We know that there are sex differences in the risk for certain types of arrhythmias. The study reveals a new factor that may contribute to different arrhythmia susceptibility between men and women,” Caldwell said.