Time-course of hormonal induction of mitochondrial glycerophosphate dehydrogenase biogenesis in rat liver

Abstract

Thyroid hormones are important regulators of mitochondrial metabolism.Due to their complex mechanism of action,the timescale of different responses varies from minutes to days.We studied selective T3 induction of the inner mitochondrial membrane enzyme-glycerophosphate dehydrogenase (mGPDH)in liver of euthyroid rats.We correlated kinetics of T3 level in blood,the mRNA level in liver,the activity and amount of mGPDH in liver mitochondria after a single dose of T3.mGPDH mRNA increased relatively fast (max.after 12 h)and fell to control level after 72 h.An increase of mGPDH activity could be already found mitochondria after 6 h and reached a maximum after 24 h in accordance with the increase in mGDH content.After 72 h,the mGPDH activity showed a significant 30% decrease.When the rats received three subsequent doses of T3,the increase of mGPDH activity was 2-fold higher than after a single T3 dose.The resuls indicate a rather short half-life of this inner mitochondrial enzyme.