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 193

cut, since both eNOS level and NO ∗ were measured pair wise ex vivo. While preg-
nancy increased eNOS protein levels in the UA endothelium, and hypoxia increased
the expression further still, increases in NO ∗ were far greater than the associated
increases in eNOS protein.
The development of the in vitro UAEC model in 1996 gave the clearest direct
evidence for the ability to remap cell signaling in UA endothelium was largely
responsible for enhancement of NO production in vivo. In maintaining NP-UAEC
or P-UAEC to the fourth passage the different expression levels of eNOS are
greatly reduced [3] and yet the ability of the cells to produce NO ∗ in response
to a number of agonists was still clearly different, with P-UAEC production of
NO ∗ being greater than NP-UAEC [3, 6]. Initial studies also showed that ATP in
particular could elicit a strong initial [Ca 2+ ]i response (the first peak within the
first minute of a 5 min observation time) in both NP-UAEC and P-UAEC but also
that the response in P-UAEC was thereafter generally more sustained above basal
(Fig. 11.1), apparently mediated by a G-protein coupled receptor and coupled to
Fig. 11.1 Representative average [Ca 2+ ]i responses to ATP (100 μ M) in NP- and P-UAEC. Dishes
of cells at 70% confluency were imaged 'full field' so an average response was obtained for each
dish of cells, rather than an individual cell response. Comparison of P-UAEC with NP-UAEC
showed quite clearly the difference in duration of the overall responses over a 30 min period.
For clarity, data are normalized to the maximum in the initial peak and each data point shown is
every 10th data point collected from n = 8 dishes, each for both NP- and P-UAEC. Lines indicate
regression fits for the acute and sustained phases. Note that the up slopes of the initial peaks are
virtually identical. The regression lines for the down slopes of the initial peaks begin to disassociate
and the regression lines for the sustained phase are completely different, with the sustained phase
of the [Ca 2+ ]i response far less pronounced in NP-UAEC. Periods of time referred to as 'acute'
phase and 'sustained' phase are indicated by bars. The arrow indicates the time of addition of ATP
to the dish (90 s)