title: Histamine H1-receptor-mediated calcium influx in DDT1MF-2 cells.
abstract: Undifferentiated monolayers of the hamster vas deferens smooth-muscle cell line, DDT1MF-2, were grown on glass coverslips and loaded with the Ca(2+)-sensitive fluorescent dye fura-2. Stimulation with histamine produced a rapid and maintained increase in intracellular free Ca2+ ([Ca2+]i), with an EC50 of 7.0 +/- 0.7 microM. The initial rise in [Ca2+]i can be attributed to Ca2+ release from intracellular stores, whereas the maintained or plateau phase is due to influx of extracellular Ca2+. The Ca2+ influx associated with the plateau phase required the continued presence of histamine on the receptor, since the H1-antagonist mepyramine (10 microM) attenuated the rise in [Ca2+]i observed when extracellular Ca2+ was re-applied after the cells had been stimulated with histamine, in experiments performed in nominally Ca(2+)-free buffer. Pretreatment with the inorganic Ca(2+)-channel blockers Ni2+ (1 mM) and Co2+ (1 mM) inhibited the influx component, whereas the organic voltage-operated Ca(2+)-channel antagonists nifedipine (10 microM) and PN-200-110 (10 microM) had no effect. These data suggest that histamine stimulates Ca2+ influx through an H1-receptor-activated Ca2+ channel. Experiments with Mn2+ indicated that the receptor-mediated Ca(2+)-influx pathway(s) is impermeable to Mn2+. Furthermore, the refilling of Ca2+ stores can occur independently of H1-receptor-mediated influx, since store refilling can be demonstrated even when the receptor-mediated Ca2+ entry is blocked by mepyramine. In conclusion, H1-receptor activation in the smooth-muscle cell line DDT1MF-2 stimulates both release of Ca2+ from intracellular stores [inositol 1,4,5-triphosphate (InsP3)-mediated] and Ca2+ influx through a receptor-activated Ca2+ channel. The subsequent refilling of the InsP3-sensitive intracellular Ca2+ store is independent of histamine H1-receptor stimulation (mepyramine-insensitive) and occurs without an observable rise in cytosolic free Ca2+.
authors.affiliation: Department of Physiology and Pharmacology, Medical School, Queen's Medical Centre, Nottingham, U.K.
authors.forename: J M
authors.initials: JM
authors.lastname: Dickenson
authors.forename: S J
authors.initials: SJ
authors.lastname: Hill
mesh_terms: D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002413:Cations, Divalent; D002460:Cell Line; D006224:Cricetinae; D006632:Histamine / Q000378:metabolism; D008297:Male; D008345:Manganese / Q000494:pharmacology; D009130:Muscle, Smooth / Q000378:metabolism; D009532:Nickel / Q000494:pharmacology; D011738:Pyrilamine / Q000494:pharmacology; D011969:Receptors, Histamine H1 / Q000187:drug effects / Q000378:metabolism*; D014649:Vas Deferens / Q000378:metabolism
chemical_list: D002121:Calcium Channel Blockers; D002413:Cations, Divalent; D011969:Receptors, Histamine H1; D008345:Manganese; D009532:Nickel; D006632:Histamine; D011738:Pyrilamine; D002118:Calcium