title: Isoproterenol-stimulated taurine influx in the perfused rat heart.
abstract: Taurine influx in the perfused rat heart was characterized and the effect of isoproterenol on this process determined. Hearts were perfused by the Langendorff technique with [3H]-taurine in a non-recirculating system. The rate of taurine influx was constant for at least 20 min and the process was saturable. A Km of 45 micron indicated that taurine influx is mediated by a high affinity transport system. Competition between taurine and beta-alanine, but not alpha-amino acids, for influx indicated that the transport sites are specific for beta-amino acids. Isoproterenol (4 X 10(-7) M) stimulated the rate of taurine influx, but propranolol (1 X 10(-8) M) blocked this stimulation. The enhancement of influx by isoproterenol was specific for beta-amino acids in that alpha-amino acid influx was not affected. Dibutyryl cyclic AMP (1 X 10(-3) M) and theophylline (1 X 10(-3) M) also stimulated taurine influx, whereas alterations in heart rate had no effect on the rate of taurine influx. The results are suggestive of a beta-adrenergically activated, cyclic AMP-mediated mechanism controlling isoproterenol-stimulated taurine influx.
mesh_terms: D000409:Alanine / Q000502:physiology; D000596:Amino Acids / Q000502:physiology; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D003994:Bucladesine / Q000494:pharmacology; D006321:Heart / Q000187:drug effects / Q000502:physiology; D007545:Isoproterenol / Q000494:pharmacology*; D009206:Myocardium / Q000378:metabolism*; D010477:Perfusion; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D013654:Taurine / Q000378:metabolism*; D013806:Theophylline / Q000494:pharmacology
chemical_list: D000596:Amino Acids; D013654:Taurine; D003994:Bucladesine; D011433:Propranolol; D013806:Theophylline; D007545:Isoproterenol; D000409:Alanine