title: Nordihydroguaiaretic acid elevates osteoblastic intracellular Ca2+.
abstract: Nordihydroguaiaretic acid (NDGA) is widely used as a pharmacological tool to inhibit lipoxygenases; however, recent evidence suggests that it increases renal intracellular [Ca2+]i via novel mechanisms. Here the effect of NDGA on Ca2+ signaling in MG63 osteoblastic cells was explored using fura-2 as a Ca2+ indicator. NDGA (2-50 microM) increased [Ca2+]i in a concentration-dependent manner. The signal comprised an initial rise and an elevated phase over a time period of 4 min. Removing extracellular Ca2+ reduced 2-50 microM NDGA-induced signals by 62+/-2%. After incubation with 50 microM NDGA in Ca2+-free medium for several minutes, addition of 3 mM CaCl2 induced an increase in [Ca2+]i. NDGA (50 microM)-induced [Ca2+]i increases were not changed by pretreatment with 10 microM of verapamil, diltiazem, nifedipine, nimodipine and nicardipine. In Ca2+-free medium, pretreatment with the endoplasmic reticulum Ca2+ pump inhibitor thapsigargin (1 microM) inhibited 50 microM NDGA-induced [Ca2+]i increases by 69+/-3%. Inhibition of phospholipase C with 2 microM U73122 had little effect on 50 microM NDGA-induced Ca2+ release. Several other lipoxygenase inhibitors had no effect on basal [Ca2+]i. At a concentration that did not increase basal [Ca2+]i, NDGA (1 microM) did not alter 10 microM ATP- or 1 microM thapsigargin-induced [Ca2+]i increases. Alteration of protein kinase C activity with 1 nM phorbol 12-myristate 13-acetate or 2 microM GF 109203X did not affect 50 microM NDGA-induced [Ca2+]i increases. Together, the results show that NDGA increased [Ca2+]i in osteoblasts in a lipoxygenase-independent manner, by releasing stored Ca2+ in a fashion independent of phospholipase C activity, and by causing Ca2+ influx.
authors.affiliation: Department of Rehabilitation, Kaohsiung Veterans General Hospital, 386 Ta Chung 1st Road, Taipei, Taiwan 813.
authors.forename: J L
authors.initials: JL
authors.lastname: Wang
authors.forename: H J
authors.initials: HJ
authors.lastname: Chang
authors.forename: L L
authors.initials: LL
authors.lastname: Tseng
authors.forename: C P
authors.initials: CP
authors.lastname: Liu
authors.forename: K C
authors.initials: KC
authors.lastname: Lee
authors.forename: K J
authors.initials: KJ
authors.lastname: Chou
authors.forename: J S
authors.initials: JS
authors.lastname: Cheng
authors.forename: Y K
authors.initials: YK
authors.lastname: Lo
authors.forename: W
authors.initials: W
authors.lastname: Su
authors.forename: Y P
authors.initials: YP
authors.lastname: Law
authors.forename: W C
authors.initials: WC
authors.lastname: Chen
authors.forename: R C
authors.initials: RC
authors.lastname: Chan
authors.forename: C R
authors.initials: CR
authors.lastname: Jan
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects*; D002460:Cell Line; D005456:Fluorescent Dyes; D016257:Fura-2; D006801:Humans; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology*; D009637:Masoprocol / Q000494:pharmacology*; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism*
chemical_list: D002121:Calcium Channel Blockers; D005456:Fluorescent Dyes; D016859:Lipoxygenase Inhibitors; D009637:Masoprocol; D002118:Calcium; D016257:Fura-2