Erythrocytes possess an intrinsic barrier to nitric oxide consumption

Mark W. Vaughn, Kuang Tse Huang, Lih Kuo, James C. Liao

Research output: Contribution to journalArticlepeer-review

191 Scopus citations

Abstract

It has been reported that free hemoglobin (Hb) reacts with NO at an extremely high rate (K(Hb) ~107 M-1 s-1) and that the red blood cell (RBC) membrane is highly permeable to NO. RBCs, however, react with NO 500- 1000 times slower. This reduction of NO reaction rate by RBCs has been attributed to the extracellular diffusion limitation. To test whether additional limitations are also important, we designed a competition test, which allows the extracellular diffusion limitation to be distinguished from transmembrane or intracellular resistance. This test exploited the competition between free Hb and RBCs for NO generated in a homogenous phase by an NO donor. If the extracellular diffusion resistance is negligible, then the results would follow a kinetic model that assumes homogenous reaction without extracellular diffusion limitation. In this case, the measured effective reaction rate constant, K(RBC), would remain invariant of the hematocrit, extracellular-free Hb concentration, and NO donor concentration. Results show that the K(RBC) approaches a constant only when the hematocrit is greater than 10%, suggesting that at higher hematocrit, the extracellular diffusion resistance is negligible. Under such a condition, the NO consumption by RBCs is still 500-1000 times slower than that by free Hb. This result suggests that intrinsic RBC factors, such as transmembrane diffusion limitation or intracellular mechanisms, exist to reduce the NO consumption by RBCs.

Original languageEnglish
Pages (from-to)2342-2348
Number of pages7
JournalJournal of Biological Chemistry
Volume275
Issue number4
DOIs
StatePublished - Jan 28 2000

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