Selective Uptake-mechanisms in Rabbit Retinal Cells

Abstract

Abstract: : Purpose: The labeling of D1 receptors by the selective D1 antagonist BODIPY-FL SCH23390 (Molecular Probes) can be recognized by fluorescence restricted to cell surfaces (see e.g. Huemer et al ARVO 2000). But in several types of retinal cells an uptake can be shown by cytosolic distribution of the substance in confocal microscopy. The characterization of putative uptake mechanisms is purpose of this study. Methods: Rabbit retinae were isolated immediately after sacrification and transferred to cooled culture medium. The fluorescent labeled D1 antagonist BODIPY-FL SCH23390 and different uptake inhibitors were added to the medium and retinae incubated for 15 to 120 min. Then retinae were transferred to a covered chamber with the ganglion cell layer facing down and image series were taken with an inverted laser scanning confocal microscope (Argon Laser 488nm, EM 505nm) Results: BODIPY-FL SCH23390 is distributed within the cytosol of Müller cells and in a population of retinal ganglion cells. An uptake into bipolar cells is implied by our earlier study but outside the confocal focus range in whole mounts and hence could not be further examined in this study. In ganglion cells we found a dose dependent uptake inhibition of this uptake by desipramin, but not by cocaine or nomifensin. Conclusion: We can show that the use of substances like BODIPY-FL SCH23390 can indicate local uptake in addition to receptor labelling. We suggest a mechanism related to indoleamine uptake for BODIPY-FL SCH23390 as indicated by the desipramine sensitivity. A relationship to mechanisms for the in vivo uptake of transmitters is likely but has yet to be examined further.

Keywords: 554 retina • 490 neurotransmitters/neurotransmitter systems