Adrenergic stimulation of taurine transport by the heart.

A high-affinity transport system that is specific for beta-amino acids has been delineated in rat hearts. This system transports the cardiotonic sulfonic amino acid taurine. beta-Adrenergic stimulation increases the transport capacity without effect on alpha-amino acid uptake, as does stimulation with adenosine 3',5'-monophosphate or theophylline. The existence of such an uptake system for taurine in the heart accounts for the high intra- to extracellular concentration gradient that is maintained, and suggests that cardiac stress is associated with increased taurine uptake. This may explain why taurine is the only amino acid to be markedly elevated in congestive heart failure. Taurine is a modifier of calcium fluxes in the heart, as are beta-adrenergic agonists. The presence of this uptake system suggests a link between beta-adrenergic stimulation of calcium and taurine fluxes.