[Transmembrane potential of rat liver mitochondria in hypothyreosis]

Transmembrane potential in liver mitochondria of hypothyroid rats was lower than that in normal animals. In hypothyroid rat mitochondria, the system responsible for maintaining the transmembrane potential was more resistant to the disturbing action of Ca2+ions. This was manifested in both the longer period of transmembrane potential under the limited content of Ca2+ and in the increased maximal dose of Ca2+, which is required for a quick decrease in transmembrane potential. Thyroxine injection (300 micrograms/100 g mass intraperitoneally) made in 48 h almost recovered the transmembrane potential value to that in the normal animals, with a dramatic lowering of the resistance of organelles to the disturbing action of Ca2+ being observed. Apparently, the increase in the resistance of hypothyroid rat mitochondria to the disturbing action of Ca2+ is connected with a reduction in the activity of mitochondrial phospholipids and with deceleration of lipid peroxidation in the mitochondria of hypothyroid animals.