caa a22 4500 469077794 CHVBK 20180323132940.0 cr unu---uuuuu 170328e19920701xx s 000 0 eng 10.1007/BF00167576 doi (NATIONALLICENCE)springer-10.1007/BF00167576 Modulation of cytosolic free calcium concentration by α1-adrenoceptors in rat atrial cells [Elektronische Daten] [Ulrich Jahnel, Hermann Nawrath, Ru-Chi Shieh, Virendra Sharma, Daniel Williford, Shey-Shing Sheu] Summary: The effects of α1-adrenoceptor stimulation by phenylephrine (PE) and β-adrenoceptor stimulation by isoprenaline (ISO) on Ca2+ current (ICa) and free intracellular Ca2+ concentration ([Ca2+]i) were studied in isolated atrial myocytes from rat hearts. PE did not significantly affect the magnitude of ICa, whereas large increases of peak ICa were observed in response to ISO. In electrically driven cells, PE evoked a concentration-dependent, gradual increase in diastolic [Ca2+]i and, initially, an increase in the height of peak [Ca2+]i transients. When the diastolic [Ca2+]i was increased to a greater extent, the amplitude of [Ca2+]i transients was decreased. Simultaneous measurements of [Ca2+]i and membrane potential showed that the increase in diastolic [Ca2+]i was associated with a depolarization of the membrane, and the greater amplitude of [Ca2+]i transients with a prolongation of the action potential (AP). The PE-induced increase in diastolic [Ca2+]i was eliminated when the cells were voltage-clamped at the original resting membrane potential (RP); under these conditions, an increase in [Ca2+]i transients was observed in response to PE. ISO usually caused larger increases in the amplitude of [Ca2+]i transients with only minor changes in diastolic [Ca2+]i. These results suggest that PE and ISO increase the amplitude of [Ca2+]i transients in rat atrium in different ways. The increase in [Ca2+]i transients in response to β-adrenoceptor stimulation is commonly thought to be mediated by a greater conductance of voltage-dependent Ca2+ channels causing a greater Ca2+ influx and a release of more Ca2+ from the sarcoplasmic reticulum during the AP. The increase in diastolic [Ca2+]i in response to PE is probably a consequence of the depolarization of the membrane, possibly involving the voltage-dependent Na+-Ca2+ exchange mechanism. The increase in the amplitude of the [Ca2+]i transients in response to PE may be ascribed both to the initial increase in diastolic [Ca2+]i and the prolongation of the AP. Springer-Verlag, 1992 Intracellular Ca2+ concentration nationallicence Fura-2 nationallicence Ca2+ current nationallicence Phenylephrine nationallicence Isoprenaline nationallicence Jahnel Ulrich Pharmakologisches Institut der Universität Mainz, Obere Zahlbacher Strasse 67, W-6500, Mainz, Federal Republic of Germany aut Nawrath Hermann Pharmakologisches Institut der Universität Mainz, Obere Zahlbacher Strasse 67, W-6500, Mainz, Federal Republic of Germany aut Shieh Ru-Chi Department of Pharmacology, University of Rochester, School of Medicine and Dentistry, Rochester, NY, USA aut Sharma Virendra Department of Pharmacology, University of Rochester, School of Medicine and Dentistry, Rochester, NY, USA aut Williford Daniel Department of Pharmacology, University of Rochester, School of Medicine and Dentistry, Rochester, NY, USA aut Sheu Shey-Shing Department of Pharmacology, University of Rochester, School of Medicine and Dentistry, Rochester, NY, USA aut Naunyn-Schmiedeberg's Archives of Pharmacology Springer-Verlag 346/1(1992-07-01), 88-93 0028-1298 346:1<88 1992 346 210 https://doi.org/10.1007/BF00167576 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00167576 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Jahnel Ulrich Pharmakologisches Institut der Universität Mainz, Obere Zahlbacher Strasse 67, W-6500, Mainz, Federal Republic of Germany aut NATIONALLICENCE 700 1- Nawrath Hermann Pharmakologisches Institut der Universität Mainz, Obere Zahlbacher Strasse 67, W-6500, Mainz, Federal Republic of Germany aut NATIONALLICENCE 700 1- Shieh Ru-Chi Department of Pharmacology, University of Rochester, School of Medicine and Dentistry, Rochester, NY, USA aut NATIONALLICENCE 700 1- Sharma Virendra Department of Pharmacology, University of Rochester, School of Medicine and Dentistry, Rochester, NY, USA aut NATIONALLICENCE 700 1- Williford Daniel Department of Pharmacology, University of Rochester, School of Medicine and Dentistry, Rochester, NY, USA aut NATIONALLICENCE 700 1- Sheu Shey-Shing Department of Pharmacology, University of Rochester, School of Medicine and Dentistry, Rochester, NY, USA aut NATIONALLICENCE 773 0- Naunyn-Schmiedeberg's Archives of Pharmacology Springer-Verlag 346/1(1992-07-01), 88-93 0028-1298 346:1<88 1992 346 210 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer