Reduction in mitochondrial membrane peroxidizability index…
619
linked (glutamate/malate) and complex II-‐linked (succinate + rotenone)
substrates (Table 1). No significant differences were detected with both substrates
in the state 4 and 3 between atenolol and control groups. However, the rate of
oxygen consumption was higher in the phosphorylating state than in the resting
state with all the substrates used, indicating the good functionality and tight
coupling of the mitochondria.
Table 1.-‐
Rates of oxygen consumption of heart mitochondria from control or atenolol treated
Wistar rats.
CONTROL
ATENOLOL
Glutamate/malate (State 4)
60.8 ± 8.3
60.0±4.8
Glutamate/malate (State 3)
203.1±30.4
189.2±11.8
Glutamate/malate (RCI)
3.5±0.5
3.2±0.3
Succinate+rotenone (State 4)
135.9±9.4
135.1±11.3
Succinate+rotenone (State3)
357.3±22.7
364.2±31.9
Succinate+rotenone (RCI)
2.7±0.1
2.7±0.1
Values are means ± SEM (nmoles of O
2
/ min
.
mg protein) from 6-‐8 different samples per group.
State 4: oxygen consumption in the absence of ADP. State 3: oxygen consumption in the presence of
500µM ADP. RCI: Respiratory control index.
The mitochondrial ROS (mitROS) generation rate showed a non-‐significant
trend to decrease in the atenolol group with complex I-‐linked substrates
(glutamate/malate) but not with succinate+rotenone (Table 2). Maximum rates of
ROS generation were assayed in the presence of pyruvate/malate+rotenone
(maximum complex I ROS production) and succinate+rotenone+antimycin A
(maximum complex III ROS production). No significant differences between groups
were found either for maximum complex I or complex III generation rates.
Table 2.-‐
Basal and maximum rates of ROS production of heart mitochondria from control or
atenolol treated Wistar rats in the presence of different substrates and inhibitors of the
mitochondrial respiratory chain.
CONTROL
ATENOLOL
Glutamate/malate
0.125±0.02
0.076±0.02
Succinate
1.08±0.24
1.37±0.40
Succinate+rotenone
1.34±0.25
1.43±0.26
Glutamate/malate+rotenone
2.67±0.47
2.98±0.51
Succinate+rotenone+Antimycin A
7.04±0.85
6.96±0.83
Values are means ± SEM (nmoles of H
2
O
2
/ min mg protein) from 6-‐8 different samples per group.
Values with glutamate/malate+rotenone or succinate+rotenone+antimycin A estimate maximum
mitochondrial ROS production from complex I and III respectively. The rest of the values represent
basal rates of ROS generation at complex I (with glutamate/malate in forward and with succinate in
reverse electron flow) or at complex III (with succinate, and with succinate+rotenone).
