ATP Release Via Connexin Hemichannels Controls Intercellular Propagation of Ca Waves in Corneal Endothelial Cells - Extracellular ATP and Adenosine as Regulators of Endothelial Cell Function - page 168

Fig. 10.3 Reduced Ca 2+ wave propagation in the presence of purinergic modulators: Cells were
treated with suramin (200

M), apyrase VI (10 U/ml), apyrase VII (10 U/ml), or apyrase VI+VII
(5 U/ml each) for 30 min. The Ca 2+ wave propagation in response to mechanical stimulation is
represented in control ( black bars )( N

μ

= 53), suramin ( striped bars )( N = 42), apyrase VI ( light grey

bars )( N 21)

treated cells. Panel A shows the bar graph of the maximal normalized fluorescence (NF) and panel
B the bar graph of the percentage responsive cells (%RC) for MS and neighboring (NB) cell layers
NB1 to NB4. Panel C shows the active areas (AA) for the different experimental conditions. ∗ p <
0.05 vs. control. From [44] with permission. Copyright: Association for Research in Vision and
Ophthalmology

= 25), apyrase VII ( dark grey bars )( N = 17), and apyrase VI+VII ( dotted bars )( N =

of the ectonucleotidase inhibitor ARL-67156 (100 M) significantly enhanced the

active area of the Ca 2+ wave. These data provide evidence that PIC via an agonist
of P2 receptors is involved in the IC [44].
Brilliant Blue G (BBG), a selective antagonist for P2X7-receptors [50], which at
higher concentrations also inhibits other P2X receptors such as P2X4 and P2X5, had
no significant influence on the propagation of the Ca 2+ wave. In contrast, the PLC
inhibitor U-73122 (10

μ

M) caused a marked reduction of the wave propagation,
providing evidence that the P2 receptors involved belong to the class of PLC

μ

-
coupled P2Y receptors. We can therefore conclude that the purinergic receptors
that are mainly responsible for the paracrine intercellular Ca 2+ wave propagation
in BCEC are of the P2Y subtype.

β