The purpose of this study was to investigate the decline in rat liver mitochondria respiration found in adult rats compared to younger ones, and to find a link between this respiratory impairment and a tissue hypothyroidism state. To this end, hepatic concentration and serum levels of triiodothyronine were measured in postpubertal rats (60 days old) and adult rats (180 days old). In addition, in these rats we measured oxidative phosphorylation in homogenate together with coupled and uncoupled respiration in isolated mitochondria using succinate or durohydroquinone as substrate. We found that mitochondria from adult rats consumed less oxygen compared to younger rats due to lower electron transport chain and phosphorylating system activity. In addition, we found that in state 4 condition, mitochondria from adult rats consumed less oxygen than mitochondria from young rats. Finally, we found a decrease in liver triiodothyronine concentration in adult rats.
In conclusion, the results of this study show that hepatic mitochondria in adult rats have a decreased ATP synthesis capacity and proton permeability, both consistent with the tissue hypothyroidism found in the liver of adult rats.
Key words:
Homogenate Respiration - Mitochondrial Protein Mass - Uncoupled Respiration - Cytochrome Content - Serum Triiodothyronine Level
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