Nitrite May Be an
Important EDRF Modulator
TIAN Ya-Ping
( Department of Clinical Biochemistry, Chinese PLA General Hospital,
Beijing 100853, China )
Rokicinski M. and Betts W.H.
( Rheumatology Unit, the Queen Elizabeth Hospital, Adelaide, SA 5011,
Australia )
Abstract Recently many studies
suggested that S-nitrosothiols instead of active nitric oxide are EDRF. The
studies showed that reduced thiols could not react directly with ・NO at
physiological pH (7.4) to form S-nitrosothiols, but oxidized to nitrite which
is very stable at pH 7.4. In contrast, at low pH, nitrite reacted rapidly with
reduced thiols to form S-nitrosothiols. Similarly, both nitrite and ・NO gas
reacted with deoxyHb and oxyHb at low pH, but not at pH 7.4, to form HbFeII-NO
complex or metHb and nitrate. The pH is a key factor to control this
nitrosation process which is determined in vivo by oxygen tension and
redox status. From these results a hypothesis is proposed that nitrite may be
an EDRF modulator, which controls the nitrosation level of reduced thiols in
biological system.
Key Words Nitrite; S-nitrosothiols; pH; reduced
thiols; hemoglobin
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