Gs protein-coupled receptors in human heart

Endogenous amines, such as the neurotransmitter noradrenaline or humoral adrenaline, 5-hydroxytryptamine (5-HT) and histamine, enhance the rate and force of the heart beat. These amines act as agonists at specific membrane receptors that are usually coupled to the Gs protein which, in turn, usually uses adenylyl cyclase as an effector. Activation of some of these receptors can be beneficial or harmful to heart function. Some interesting properties of these cardiac receptors will be discussed, particularly their function in human heart. A vast array of cardiac tissues and cells from animals have been used as models of human heart function. Surprisingly, extrapolations and inferences about receptor-mediated modulation of human heart function from results obtained from animal cardiac tissues and cells can be misleading, resulting in the need for direct experimentation on human heart tissues and cells. The aim of this article is to concentrate on quantitative aspects of the function of coexisting Gs protein-coupled receptors in human heart to ascertain their relative importance. The value of choice of relevant animal models is critically stressed. The function of individual receptors will be compared first, followed by some indirect evidence for cross-talk among Gs-coupled receptors.