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GH 3 Cells, Ionic Currents and Cell Killing: Photomodification Sensitized by Rose Bengal
Author(s) -
Valenzeno Dennis Paul,
Tarr Merrill
Publication year - 1998
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1998.tb02508.x
Subject(s) - rose bengal , chemistry , trypan blue , calcein , potassium , biophysics , pipette , membrane potential , potassium channel , calcium , cell , membrane , biochemistry , biology , organic chemistry
Photosensitization using Rose Bengal (RB) modifies membrane ionic currents and kills cultured mouse pituitary, GH 3 , cells. Here we investigate the dose‐response relationship for ionic current modification and for cell killing to assess a possible causal link. When exposed to 0.5 μM RB and 6.5 mW/cm 2 of visible light, calcium current was blocked in 1.9 ± 0.2 min (meanSEM; 0.74 ± 0.08 J/ cm 2 ; n = 18), a transient component of potassium current, tentatively identified as a delayed‐rectifier potassium current, disappeared in 52 ± 8 s (0.34 ± 0.05 J/cm 2 ; n = 10) and a steady‐state component of potassium current, largely a calcium‐activated potassium current, disappeared in 3.5 ± 0.4 min (1.37 ± 0.16 J/cm 2 ; n = 11). Conversely, the background leak current increased in magnitude. At 5 min of illumination, the longest time studied here, it continued to increase nearly linearly, making it the only current component studied that is still changing after 5 min of light. Under the conditions used, cell killing increased to 100% in the exposure range of4–10 min of illumination (1.6 J/cm 2 to 3.9 J/cm 2 ) when assessed using fluorescent markers, ethidium homodimer and calcein and required slightly longer exposure times when assessed using trypan blue. Thus, it is difficult to ascribe a causal role in cell killing by photosensitization to alterations of standard ion channels and known ionic currents. However, the increase in leak current has the correct dose‐response characteristics to be involved.