Identification of Three Isoforms of the InsP3 Receptor in Human Myometrial Smooth Muscle
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The mechanisms responsible for the mobilisation of Ca2+ from intracellular stores sensitive to inositol trisphosphate (InsP3) were studied in saponin-permeabilised human myometrial cells in which the sarcoplasmic reticulum was pre-loaded with 45Ca2+. InsP3-induced 45Ca2+ release was measured over the InsP3 concentration range of 100 nM to 100 microM and showed a graded response. InsP3-induced 45Ca2+ release was inhibited by heparin (20-40 microg/ml) but not significantly affected by caffeine. The Ca2+ sensitivity of InsP3-induced Ca2+ release was measured under conditions which were designed to exclude interference with Ca2+ released by the ryanodine receptor/channel complex. The data showed a bell-shaped relationship with the InsP3 receptor (InsP3R) functional at 10 nM, becoming maximally activated at 300 nM but inhibited at 10 microM Ca2+. Messenger RNA encoding for three isoforms of InsP3R, type I, II and type III, was shown to be present. The relative expression levels of these messengers were obtained by ratio-PCR analysis and the levels of expression of the different isoforms were found to differ between individual patients.
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Inositol trisphosphate receptors in smooth muscle cells.
Narayanan D, Adebiyi A, Jaggar J Am J Physiol Heart Circ Physiol. 2012; 302(11):H2190-210.
PMID: 22447942 PMC: 3378287. DOI: 10.1152/ajpheart.01146.2011.
Lipid rafts, the sarcoplasmic reticulum and uterine calcium signalling: an integrated approach.
Noble K, Zhang J, Wray S J Physiol. 2005; 570(Pt 1):29-35.
PMID: 16239270 PMC: 1464295. DOI: 10.1113/jphysiol.2005.098475.
Nuclear and cytosolic calcium are regulated independently.
Leite M, Thrower E, Echevarria W, Koulen P, Hirata K, Bennett A Proc Natl Acad Sci U S A. 2003; 100(5):2975-80.
PMID: 12606721 PMC: 151451. DOI: 10.1073/pnas.0536590100.
Regulation of the type III InsP(3) receptor by InsP(3) and ATP.
Hagar R, Ehrlich B Biophys J. 2000; 79(1):271-8.
PMID: 10866953 PMC: 1300931. DOI: 10.1016/S0006-3495(00)76289-8.