Mitochondrial Ca
2+
is increased by IP
3
R agonists. (
A
) Original confocal recordings obtained from WT and transgenic (sponge) myocytes stimulated with 10 nM ET-1 ± 3 µM 2-APB (red: WT, ET-1 alone; black: WT, ET-1 + 2-APB; grey: TG, ET-1 alone) for 20 min. (
B
) Mean values of resulting mitochondrial Ca
2+
(Ca
2 +m
) changes induced by ET-1 in WT mice in the absence (
n
= 27 from seven animals) or presence of 2-APB (
n
= 19 from four animals) and in IP
3
sponge mice [colours same as in (
A
)]. (
C
) Original confocal recordings of myocytes stimulated with 3 µM Ang II ± 3 µM 2-APB (green: Ang II; black: Ang II + 2-APB). (
D
) Mean values of resulting Ca
2 +m
changes induced by Ang II in the absence (
n
= 10 from three animals) or presence of 2-APB (
n
= 5 from two animals) [colours same as in (
C
)]. Both IP
3
agonists evoked a significant increase in Ca
2 +m
, respectively. This increase could be blocked effectively by 3 µM of the IP
3
receptor blocker 2-APB and was abolished in IP
3
-sponge mice. (
E
) Original confocal recordings of WT and transgenic (sponge) myocytes stimulated with 500 nM ISO ± 3µM 2-APB (blue: WT, ISO alone; black: WT, ISO + 2-APB) for 20 min. (
F
) Mean values of Ca
2 +m
changes induced by ISO in the absence (
n
= 10 from three animals) or presence of 2-APB (
n =
8 from two animals) [colours same as in (
E
)]. The smaller peak and different time course indicate different underlying mechanisms. (
G
) Original confocal recordings obtained from electrically stimulated (0.5 Hz) WT myocytes stimulated with 10 nM ET-1 ± 3 µM 2-APB (red: ET-1 alone; black: ET-1 + 2-APB) or ISO ± 3 µM 2-APB (blue: ISO alone; grey: ISO + 2APB) for 20 min. (
H
) Mean values of resulting mitochondrial Ca
2+
(Ca
2 +m
) changes induced by ET-1 and ISO in WT mice in the absence (ET-1:
n
= 6 from three animals; ISO:
n
= 7 from two animals) or presence of 2-APB (ET-1 + 2-APB:
n
= 5 from three animals; ISO + 2-APB:
n
= 11 from two animals) [colours same as in (
G
)]. (
I
) Mean values of cytosolic Ca
2+
levels (Ca
2 +i
) in mouse myocytes measured with the Ca
2+
-sensitive probe fluo-4. The myocytes were stimulated with ET-1 (red) or ISO (blue), respectively, demonstrating that both agonists induced a stable increase of Ca
2 +i
. *
P
< 0.05 compared with untreated control using ANOVA Dunnett’s test; **
P
< 0.01 compared with untreated control ANOVA Dunnett’s test.