Calcium uptake in rat liver mitochondria accompanied by activation of ATP-dependent potassium channel.
The influence of potassium ions on calcium uptake in rat liver mitochondria is studied. It is shown that an increase in K+ and Ca2+ concentrations in the incubation medium leads to a decrease in calcium uptake in mitochondria together with a simultaneous increase in potassium uptake due to the potential-dependent transport of K+ in the mitochondrial matrix. Both effects are more pronounced in the presence of an ATP-dependent K+-channel (K+(ATP)-channel) opener, diazoxide (Dz). Activation of the K+(ATP)-channel by Dz alters the functional state of mitochondria and leads to an increase in the respiration rate in state 2 and a decrease in the oxygen uptake and the rate of ATP synthesis in state 3. The effect of Dz on oxygen consumption in state 3 is mimicked by valinomycin, but it is opposite to that of the classical protonophore uncoupler CCCP. It is concluded that the potential-dependent uptake of potassium is closely coupled to calcium transport and is an important parameter of energy coupling responsible for complex changes in oxygen consumption and Ca2+-transport properties of mitochondria.
Akopova
O V
OV
Bogomolets Institute of Physiology, National Academy of Sciences of Ukraine, Kiev, Ukraine. circul@biph.kiev.ua
Nosar
V I
VI
Mankovskaya
I N
IN
Sagach
V F
VF
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000378:metabolism; D054086:KATP Channels / Q000378:metabolism*; D007700:Kinetics; D008930:Mitochondria, Liver / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D011188:Potassium / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D054086:KATP Channels; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D000255:Adenosine Triphosphate; D011188:Potassium; D002118:Calcium