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Dayu Li, Richard B. Carozza, Marie A. Shatos, Robin R. Hodges, Darlene A. Dartt; Effect of Histamine on Ca2+-Dependent Signaling Pathways in Rat Conjunctival Goblet Cells. Invest. Ophthalmol. Vis. Sci. 2012;53(11):6928-6938. doi: 10.1167/iovs.12-10163.
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The purpose of this study was to determine the Ca2+-dependent cellular signaling pathways used by histamine to stimulate conjunctival goblet cell secretion.
Cultured rat goblet cells were grown in RPMI 1640. Goblet cell secretion of high molecular weight glycoconjugates was measured by an enzyme-linked lectin assay. Intracellular [Ca2+] ([Ca2+]i) was measured by loading cultured cells with the Ca2+ sensitive dye fura-2. The level of [Ca2+]i was measured using fluorescence microscopy. Extracellular regulated kinase (ERK) 2 was depleted using small interfering RNA (siRNA).
Histamine-stimulated conjunctival goblet cell secretion of high molecular weight glycoproteins was blocked by removal of extracellular Ca2+ and depletion of ERK2 by siRNA. Histamine increase in [Ca2+]i was desensitized by repeated addition of agonist and blocked by a phospholipase C antagonist. Histamine at higher doses increased [Ca2+]i by stimulating influx of extracellular Ca2+, but at a lower dose released Ca2+ from intracellular stores. Activation of each histamine receptor subtype (H1–H4) increased [Ca2+]i and histamine stimulation was blocked by antagonists of each receptor subtype. The H2 receptor subtype increase in [Ca2+]i was cAMP dependent.
We conclude that histamine activates phospholipase C to release intracellular Ca2+ that induces the influx of extracellular Ca2+ and activates ERK1/2 to stimulate conjunctival goblet cell mucous secretion, and that activation of all four histamine receptor subtypes can increase [Ca2+]i.
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