Ontogeny of purinergic receptor-regulated Ca2+ signaling in mouse cortical collecting duct epithelium

Changes in ATP-induced increase in {[}Ca2+], during collecting duct
ontogeny were studied in primary monolayer cultures of mouse
ureteric bud (UB) and cortical collecting duct (CCD) cells by
Fura-PE3 fluorescence ratio imaging. In UB (embryonic day E14 and
postnatal day P1) the ATIP-stimulated increase (EC50 approximate to
1 muM) in fluorescence ratio (DeltaR(ATP)) was independent of
extracellular Ca2+ and insensitive to the P2
purinoceptor-antagonist suramin (1 mM). From day P7 onward when CCD
morphogenesis had been completed DeltaR(ATP) increased and became
dependent on extracellular Ca2+. This ATP-stimulated Ca2+ entry
into CCD cells was non-capacitative and suramin (11 mM)insensitive,
but sensitive to nifedipine (30 muM) and enhanced by Bay K8644 (15
muM), a blocker and an agonist of L-type Ca2+ channels,
respectively. Quantitative RT-PCR demonstrated similar mRNA
expression of L-type Ca2+ channel alpha1-subunit, P2Y(1), P2Y(2),
and P2X(4b) purinoceptors in UB and CCD monolayers while the
abundance of P2X(4) mRNA increased with CCD morphogenesis. In
conclusion, both embryonic and postnatal cells express probably
P2Y(2)-stimulated Ca2+ release from intracellular stores. With
development, the CCD epithelium acquires ATP-stimulated Ca2+ entry
via L-type Ca2+ channels. This pathway might by mediated by the
increasing expression of P2X(4)-receptors resulting in an
increasing ATP-dependent membrane depolarization and activation of
L-type Ca2+ channels. Copyright (C) 2002 S. Karger AG, Basel.