Erythrocyte consumption of nitric oxide: Competition experiment and model analysis

It is generally believed that the erythrocyte membrane is highly permeable to nitric oxide (NO). To prevent NO from freely entering and being scavenge d by the red blood cell (RBC), it has been suggested that NO consumption is limited by the mass transfer resistance of the diffusion layer adjacent to the erythrocyte membrane. Recently, we (Vaughn et al. (2000). J. Biol. Che m. 275, 2342) presented an experimental technique that overcomes experiment al diffusional limitations and showed that RBCs also possess a mechanism to slow nitric oxide uptake. Here, we present a mathematical analysis of this technique by modeling the NO uptake of a single cell. We obtain additional data (n = 33, total) by use of the competition experiment and, through app lication of the model, show that either the RBC membrane permeability to NO or the intracellular reaction rate between NO and hemoglobin (Hb) is at le ast 2000-fold lower than previously thought. As a result, RBCs react with N O at a rate three orders of magnitude slower than free oxyHb. This phenomen a may play an important role in NO bioitvailability. (C) 2001 Academic Pres s.