Abstract
Extraneuronal catecholamine uptake was investigated in isolated quiescent rat myocardial cells. By administration of (3H-)(−)noradrenaline concentration of 22 nmol/l up to 1000 μmol/l the following data were obtained: (1) The KM of the uptake process amounted to 260 μmol/l, the Vmax to 4.24 nmol/(10 min × mg Protein) corresponding to 179 nmol/(min × gWWt)(WWT = Wet Weight). (2) The uptake was largely inhibited by the uptake2-inhibitors corticosterone (100 μmol/l), isoprenaline (IC so = 30.6 μmol/l), and O-methylisoprenaline (IC50 = 2.1 pmol/l), but not by the uptake1-inhibitors cocaine (100 μmol/l) and desipramine (10 μmol/l). (3) The ‘affinity’-values KM and IC50 closely agreed with those already known, but the Vmax-value was higher than those obtained in whole rat hearts by a factor of at least 1.79. This is caused presumably by the voltage dependence of the uptake mechanism and the resulting inhibition of uptake 2 during the periods of depolarisation in beating hearts of other studies.
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Obst, O.O., Rose, H. & Kammermeier, H. Characterization of catecholamine uptake2 in isolated cardiac myocytes. Mol Cell Biochem 163, 181–183 (1996). https://doi.org/10.1007/BF00408656
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DOI: https://doi.org/10.1007/BF00408656