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.
Fisch
C
C
INSERM Unité 24, Clichy, France.
Robin
M A
MA
Letteron
P
P
Fromenty
B
B
Berson
A
A
Renault
S
S
Chachaty
C
C
Pessayre
D
D
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