THE INFLUENCE OF CALCIUM ACCUMULATION ON THE FUNCTION OF ELECTRON TRANSPORT CHAIN IN THE OLD RAT HEART MITOCHONDRIA
A.Yu. Luchkova, N.A. Strutynska, V.F. Sagach
Bogomoletz Institute of Physiology, NAS Ukraine, Kyiv, Ukraine
We studied the parameters of mitochondrial respiration in
the suspension of isolated heart mitochondria from old rats
using glutamate and succinate – the substrates for the I and
II respiratory chain complexes, as well as the dependence of
this process on the action of calcium ions. It was shown that
Ca2+ influx dynamics in old rat heart mitochondria is different
from that in adult control organelles, and the maximum of
fluorescence of the calcium-sensitive dye Fluo-4 AM at Ca2+
concentration 100 μmol/l was observed at 3rd minute and
was 27% higher than in the control. Consequently, in older
rats, we observed a more sharp increase in intramitochondrial
calcium. Despite the moderate increase (using succinate) or no
different from that in adult animals (using glutamate) of the
V2 indicatorin the 24-month rats, ADP-stimulated respiration
rate decreased, which led to a decrease in respiratory control
ratio (RCR) by Chance and Lardy 1.18 and 1.6 times (with
oxidation of succinate) and 1.18 and 1.4 times (in the presence
of glutamate). However, the efficiency of phosphorylation
of ATP, which is characterized by the ratio of ATP synthesis
and oxygen absorption (ADP/O), did not change, nor did the
velocity of phosphorylation of ATP (ADP/Δt). The effect of
calcium ions on mitochondrial respiration in adult rats was
dose dependent. At low concentrations of cation (10-7 mol/l),
the Lardy’s RCR did not change, and Chance’s RCR and
ADP/O ratio significantly increased, indicating an increase in
the coupling of oxidation and phosphorylation processes. At
the same time, in the old rat heart mitochondria, calcium ions,
even at low concentrations (10-7 mol/l), did not significantly
increase the rate of respiration and the ADP/O ratio. 10-5 and
10-4 mol/l Ca2+ resulted in a partial reduction of the activity of
the respiratory chain in adult animals and significantly reduced
the ADP-stimulated respiration, and the coefficients of RCR
after Chance and Lardy in the elderly. +/Δt also tended to fall.
mitochondria; Ca2+; oxidative phosphorylation; respiratory chain; heart; aging.
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