Oxytocin mobilizes calcium from a unique heparin-sensitive and thapsigargin-sensitive store in single myometrial cells from pregnant rats.
Pfl�gers Arch. 1994-08-01; 428(1): 51-59
DOI: 10.1007/bf00374751
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1. Pflugers Arch. 1994 Aug;428(1):51-9.
Oxytocin mobilizes calcium from a unique heparin-sensitive and
thapsigargin-sensitive store in single myometrial cells from pregnant rats.
Arnaudeau S(1), Leprêtre N, Mironneau J.
Author information:
(1)Laboratoire de Physiologie Cellulaire et Pharmacologie Moléculaire, URA CNRS
1489, Université de Bordeaux II, France.
Intracellular free Ca2+ concentration ([Ca2+]i) was monitored using the
fluorescence from the dye Fura-2-AM in single myometrial cells from pregnant
rats. Oxytocin and acetylcholine applied to the cell evoked an initial peak in
[Ca2+]i followed by a smaller sustained rise which was rapidly terminated upon
removal of acetylcholine or persisted after oxytocin removal. A Ca2+ channel
blocker (oxodipine) and external Ca2+ removal decreased both the transient and
sustained rises in [Ca2+]i suggesting that Ca2+ influx through L-type Ca2+
channels participated in the global Ca2+ response induced by oxytocin. However,
the initial peak in [Ca2+]i produced by oxytocin was mainly due to Ca2+ store
release: it was abolished by inclusion of heparin [which blocks inositol
1,4,5-trisphosphate (InsP3) receptors] in the pipette (whole-cell recording mode
of patch-clamp) and external application of thapsigargin (which blocks
sarcoplasmic reticulum Ca(2+)-ATPases). In contrast, the transient Ca2+ response
induced by oxytocin was unaffected by ryanodine. Moreover, caffeine failed to
induce a rise in [Ca2+]i but reduced the oxytocin-induced transient Ca2+
response. The later sustained rise in [Ca2+]i produced by oxytocin was due to the
entry of Ca2+ into the cell as it was suppressed in external Ca(2+)-free
solution. The Ca2+ entry pathway is permeable to Mn2+ ions, in contrast to that
described in various vascular and visceral smooth muscle cells. Oxytocin-induced
Ca2+ release is blocked by the oxytocin antagonist
d(CH2)5[Tyr(Me)2,Thr4,Tyr-NH2(9)]OVT. The prolonged increase in [Ca2+]i after
oxytocin removal is rapidly terminated by addition of the oxytocin antagonist
suggesting that oxytocin dissociation from its receptor is very slow.(ABSTRACT
TRUNCATED AT 250 WORDS)
DOI: 10.1007/BF00374751
PMID: 7971161 [Indexed for MEDLINE]