抄録
The subcellular localization and adjacent pH of the α1-adrenoceptor (α1-AR) subtypes conjugated with pH sensor GFP (α1-AR/pH) were assessed using real-time imaging of living, stably expressed CHO-K1 cells. The α1B-AR/pH fluorescence was detected predominantly on the cell surface and intracellular pH distribution showed homogeneous pattern. Stimulation of the α1B-AR with norepinephrine (NE, 10−7M) led to an increase in pH, promoted rapid internalization and caused Ca2+ oscillations. α1A-AR/pH fluorescence was detected not only on the cell surface but also inside the cell and this localization was unaffected by exposure to NE during observation period. Intracellular pH on the cell surface was higher than intracellular compartment before NE. Stimulation of the α1A-AR with NE led to a decrease in pH and caused only a Ca2+ transient. The α1D-AR/pH fluorescence was detected mainly intracellularly, and this localization was unaffected by exposure to NE. Intracellular pH distribution of α1D-AR/pH was homogeneous as in α1B-AR/pH. Stimulation of the α1D-AR/pH with NE led to an increase in pH and caused Ca2+ oscillations. These data show that transfected α1-AR/pH fusion proteins are functional and that there are differences in the cellular distribution of α1-AR, agonist-mediated internalization, Ca2+ response and neighbor pH among α1-AR subtypes. These differences could contribute to the diversity in physiologic responses regulated by the α1-ARs. [Jpn J Physiol 54 Suppl:S75 (2004)]
