title: Effect of histamine on Ca(2+)-dependent signaling pathways in rat conjunctival goblet cells.
abstract: OBJECTIVE
  The purpose of this study was to determine the Ca(2+)-dependent cellular signaling pathways used by histamine to stimulate conjunctival goblet cell secretion.
  
  
  METHODS
  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 [Ca(2+)] ([Ca(2+)](i)) was measured by loading cultured cells with the Ca(2+) sensitive dye fura-2. The level of [Ca(2+)](i) was measured using fluorescence microscopy. Extracellular regulated kinase (ERK) 2 was depleted using small interfering RNA (siRNA).
  
  
  RESULTS
  Histamine-stimulated conjunctival goblet cell secretion of high molecular weight glycoproteins was blocked by removal of extracellular Ca(2+) and depletion of ERK2 by siRNA. Histamine increase in [Ca(2+)](i) was desensitized by repeated addition of agonist and blocked by a phospholipase C antagonist. Histamine at higher doses increased [Ca(2+)](i) by stimulating influx of extracellular Ca(2+), but at a lower dose released Ca(2+) from intracellular stores. Activation of each histamine receptor subtype (H(1)-H(4)) increased [Ca(2+)](i) and histamine stimulation was blocked by antagonists of each receptor subtype. The H(2) receptor subtype increase in [Ca(2+)](i) was cAMP dependent.
  
  
  CONCLUSIONS
  We conclude that histamine activates phospholipase C to release intracellular Ca(2+) that induces the influx of extracellular Ca(2+) and activates ERK1/2 to stimulate conjunctival goblet cell mucous secretion, and that activation of all four histamine receptor subtypes can increase [Ca(2+)](i).
authors.affiliation: Schepens Eye Research Institute, Massachusetts Eye and Ear, Department of Ophthalmology, Harvard Medical School, Boston, MA 02114, USA.
authors.forename: Dayu
authors.initials: D
authors.lastname: Li
authors.forename: Richard B
authors.initials: RB
authors.lastname: Carozza
authors.forename: Marie A
authors.initials: MA
authors.lastname: Shatos
authors.forename: Robin R
authors.initials: RR
authors.lastname: Hodges
authors.forename: Darlene A
authors.initials: DA
authors.lastname: Dartt
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology*; D002478:Cells, Cultured; D003228:Conjunctiva / Q000166:cytology*; D004789:Enzyme Activation; D004797:Enzyme-Linked Immunosorbent Assay; D016257:Fura-2 / Q000378:metabolism; D020397:Goblet Cells / Q000187:drug effects* / Q000378:metabolism; D006632:Histamine / Q000494:pharmacology*; D017442:Histamine Agonists / Q000494:pharmacology*; D006633:Histamine Antagonists / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000502:physiology; D008297:Male; D008856:Microscopy, Fluorescence; D009077:Mucins / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D011968:Receptors, Histamine / Q000378:metabolism; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D017442:Histamine Agonists; D006633:Histamine Antagonists; D009077:Mucins; D034741:RNA, Small Interfering; D011968:Receptors, Histamine; D006632:Histamine; D010738:Type C Phospholipases; D002118:Calcium; D016257:Fura-2