A precursor of the nitric oxide donor SIN-1 modulates the stress protein heme oxygenase-1 in rat liver

In this study the effect of increased nitric oxide (NO) production on the expression of rat liver heme oxygenase-1, an inducible stress protein responsible for the catalysis of heme to biliverdin and carbon monoxide, was investigated. Rats were injected intraperitoneally with molsidomine (SIN-10), a long acting drug that is enzymatically converted in the liver to yield the active NO-releasing agent 3-morpholinosydnonimine (SIN-1). Administration of SIN-10 resulted in a significant time- and dose-dependent increase in plasma levels of nitrite/nitrate, an index of NO release. A time course of heme oxygenase-1 mRNA levels in liver showed a gradual increase in the expression of the gene encoding for this protein, which was maximal at 4 hours and returned to normal levels by 6 hours after SIN-10 treatment. Heme oxygenase activity also increased by 50% at 4 hours and was maximal 12 hours after SIN-10 administration (63% increase over baseline). These results indicate a possible role for locally generated NO in the modulation of hepatic stress response in vivo suggesting that NO mediates cell adaptation to stress by activation of endogenous defensive mechanisms.

Postnatal development of the complexes of the electron transport chain in synaptic mitochondria from rat brain

The postnatal development of the complexes of the electron transport chain in mitochondria isolated from rat brain synaptosomes was investigated. Synaptosomal brain mitochondria were isolated from rats aged 10-60 days, and the activities of mitochondrial complex I, complex II-III, complex IV and complex V were measured. There was a significant increase in the activity of II-III from day 10 to day 15 and complex IV from day 10 to day 21, thereafter the activities of complexes I-III and IV did not change significantly. The activity of complex I did not change significantly during the period 10-60 days post partum. In synaptic mitochondria, complex V activity was higher than in non-synaptic mitochondria, whereas the activity of complex I was lower than in non-synaptic mitochondria. These data show that the complexes of the respiratory chain within synaptic mitochondria have activities different from those of non-synaptic mitochondria and may have major implications for the relative susceptibility of mitochondria in different brain cell types to neurotoxins such as MPP+, hypoxic/ischaemic damage and oxidative stress.