Pregnancy Induced Reprogramming of Endothelial Function in Response to ATP: Evidence for Post Receptor Ca Signaling Plasticity - Extracellular ATP and Adenosine as Regulators of Endothelial Cell Function - page 197

NO (inhibition 60%) - see Fig. 11.3. Closer examination reveals some interest-

ing points. First, while eNOS activity in UEAC may not be directly correlated with
the [Ca 2+ ]i level in the cell, there is no doubt that when peak and plateau [Ca 2+ ]i
are no longer allowed to increase above basal there is effective inhibition of eNOS
activity, and this is greater still (in fact almost complete) in NP than in P-UAEC.
This is consistent with reports from other endothelial cells that sustained CCE is
necessary for prolonged eNOS activation [19] but also with our previous sugges-
tion, not reviewed here, that wortmannin - sensitive kinases in particular may play
an increased but still incomplete role in Ca 2+ -independent eNOS activation during
pregnancy over that in nonpregnancy in UAEC [3, 30, 14].

∼

[Ca 2+ ] i (at peak)
[Ca 2+ ] i (at 500 s)
NO (at 500 s)

A

0.30 0.08

*

#

0.25

0.06

0.20

*

0.15 0.04

*

0.10

0.02

0.05

0.00 0.00

Luteal Follicular Pregnant

B

Ca2+

0.20 0.08

NO

0.16

0.06

0.12

0.04

0.08

*

0.02

0.04

*

0.00 0.00

2-APB + ATP

ATP

Fig. 11.3 Relationship between Ca 2+ and NO in freshly isolated UA endothelium. ( A ) Effects
of ATP (100 μ M, 500 s stimulation) on [Ca 2+ ]i and NO production in the freshly-isolated UA
endothelium. Delta F/F0 (net increment fluorescence intensity) for Fura 2 at the initial [Ca 2+ ]i
peak, or for both Fura 2 and DAF signals at 500 s of treatment with ATP (100 mM) in pregnant-,
follicular- and luteal- derived UA endothelium are shown. Data are means ± SE of UAE from 6
to8ewes. ∗ P < 0.05 vs. luteal; # P < 0.05 vs. follicular. ( B ) Effects of 2-APB (50 μ M) on ATP-
and ionomycin-induced increase of [Ca 2+ ]i and NO production in the freshly-isolated pregnant UA
endothelium. After pretreatment with 2-APB (50

μ

M) or vehicle for 10 min, UA endothelium was

stimulated with ATP (100 μ M) for 500 s. Data for Fura 2 and DAF signals at 500 s are means ±

6 animals. ∗ P < 0.05 vs. ATP alone. Figure is modified from that published

SE of UAE from n =

in [36]