Reduction of thiazine dyes by bovine pulmonary arterial endothelial cells in culture. Bongarda, Robert D., Marilyn P. Merkerb, Ryushi Shundoc Yoshiyuki Okamotoc, David L. Roerigbe, John H. Linehand, and Christopher A. Dawsonae. Department of Physiology; Medical College of Wisconsin; Milwaukee, WI 53226, Department of Anesthesiology; Medical College of Wisconsin; Milwaukee, WI 53226, Department of Pharmacology/Toxicology; Medical College of Wisconsin; Milwaukee, WI 53226, Department of Chemistry; Polytechnic University; Brooklyn, NY 11201, Biomedical Engineering Department, Marquette University; Milwaukee, WI 53233, Department of Veterans Affairs; Zablocki VAMC:, Milwaukee, WI 53295
APStracts 2:0046L, 1995.
The uptake of methylene blue (MB), and toluidine blue O (TBO) by bovine pulmonary arterial endothelial cells grown on microcarrier beads was detected as a decrease in the concentration of dye in the medium after these thiazine dyes were added to the medium surrounding the cells. Since the reduced forms of these dyes are much more lipophilic than the oxidized forms, we considered the possibility that reduction of the dyes at the cell surface might have preceded the uptake by the cells. Therefore, we studied the ability of the cells to reduce a toluidine blue O - polyacrylamide polymer (TBOP), which was too large to enter the cells in either the oxidized or reduced form. The TBO moieties of the polymer were reduced by the cells, indicating that the dyes did not have to enter the cells to be reduced, and that reduction can occur at, or near, the cell surface. The rate of TBOP reduction was about the same as the rate of uptake of the monomeric dyes, indicating that the cell surface reduction mechanism had a sufficient capacity to account for the monomer uptake by the cells. We also found that ferricyanide ion, which also did not permeate the cells, was reduced by the cells, and that external ferricyanide inhibited the monomeric MB uptake. Thus, the results with ferricyanide were also consistent with the concept that the monomeric thiazine dyes are reduced at the cell surface before the more lipophilic reduced forms are taken up by the endothelial cells. 

Received 6 December 1994; accepted in final form 2 March 1995.
APS Manuscript Number L361-4.
Article publication pending Am. J. Physiol. (Lung Cell. Mol.
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on  4 April 1995.