Cell-generated nitric oxide inactivates rat hepatocyte mitochondria in vitro but reacts with hemoglobin in vivo.
OBJECTIVE
Nitric oxide forms inactive iron-nitrosyl complexes within hepatic mitochondria in vitro. However, when formed in vivo, NO might react instead with hemoglobin. The aim of this study was to compare the effects of cell-derived NO on rat hepatocyte mitochondria in vitro and in vivo.


METHODS
First, hepatocytes were cultured in vitro for 24 hours under a porous membrane supporting macrophages that were stimulated by endotoxin. Second, hepatic macrophage hyperplasia was induced in vivo by preadministration of killed Corynebacterium parvum; 7 days later, rats received endotoxin and were killed after 6 hours. Third, mitochondria were exposed to sodium nitroprusside in vitro, washed, mixed with blood, and recovered.


RESULTS
Iron-nitrosyl complexes and hepatocyte mitochondrial dysfunction were observed in the in vitro model and prevented by an NO synthase inhibitor. In the in vivo model, however, despite a 130-fold increase in plasma nitrate levels and formation of hemoglobin-NO complexes in blood, no iron-nitrosyl complex was detected in hepatic mitochondria, and hepatic mitochondrial function was not impaired. In the third model, mitochondria lost preformed iron-nitrosyl complexes when exposed to blood.


CONCLUSIONS
Although NO reacts with hepatocyte mitochondria in vitro, in vivo it reacts with sinusoidal hemoglobin without detectable impairment of hepatic mitochondrial function.
INSERM Unité 24, Clichy, France.
C
C
Fisch
M A
MA
Robin
P
P
Letteron
B
B
Fromenty
A
A
Berson
S
S
Renault
C
C
Chachaty
D
D
Pessayre
D000818:Animals; D001790:Blood Physiological Phenomena; D002478:Cells, Cultured; D006454:Hemoglobins / Q000502:physiology*; D006854:Hydrocortisone / Q000494:pharmacology; D007501:Iron / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology*; D009589:Nitrogen Oxides / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D006454:Hemoglobins; D008070:Lipopolysaccharides; D009589:Nitrogen Oxides; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; C073661:dinitrosyl iron complex; D007501:Iron; D006854:Hydrocortisone