title: Tyrosine kinase inhibitors and Ca2+ signaling: direct interactions with fura-2.
abstract: Selective inhibitors were used to study the role of tyrosine kinases in alpha(1A)-adrenoceptor-mediated responses in transfected PC12 cells. Ca(2+) responses to noradrenaline were measured using fura-2, and the effects of genistein, tyrphostin A25, and herbimycin A were examined. Neither genistein nor herbimycin A pretreatment altered noradrenaline-induced Ca(2+) responses, although tyrphostin A25 pretreatment caused some reduction. However, acute addition of genistein quickly reversed the apparent noradrenaline response, apparently, through a direct interaction with cytoplasmic fura-2. Both genistein and tyrphostin A25, at concentrations similar to those used to inhibit tyrosine kinases, markedly reduced fluorescence of fura-2 excited by both 340 and 380 nm, and genistein also reduced the 340/380 ratio. Tyrosine kinase inhibitors did not alter noradrenaline stimulated inositol phosphate formation in alpha(1A)-PC12 cells. These results suggest that tyrosine kinases are not involved in second messenger responses to alpha(1A)-adrenoceptors, but that tyrosine kinase inhibitors can interact directly with fura-2.
authors.affiliation: Department of Pharmacology, Emory University School of Medicine, Atlanta, GA, USA.
authors.forename: A
authors.initials: A
authors.lastname: Berts
authors.forename: K P
authors.initials: KP
authors.lastname: Minneman
mesh_terms: D000818:Animals; D016227:Benzoquinones; D020013:Calcium Signaling / Q000187:drug effects*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D016257:Fura-2 / Q000378:metabolism*; D019833:Genistein / Q000494:pharmacology; D007295:Inositol Phosphates / Q000096:biosynthesis; D047029:Lactams, Macrocyclic; D009638:Norepinephrine / Q000494:pharmacology; D016716:PC12 Cells; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000502:physiology; D011809:Quinones / Q000494:pharmacology; D051381:Rats; D018340:Receptors, Adrenergic, alpha-1 / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D017828:Rifabutin / Q000031:analogs & derivatives; D013050:Spectrometry, Fluorescence; D014162:Transfection; D020032:Tyrphostins / Q000494:pharmacology
chemical_list: D016227:Benzoquinones; D004791:Enzyme Inhibitors; D007295:Inositol Phosphates; D047029:Lactams, Macrocyclic; D011809:Quinones; D018340:Receptors, Adrenergic, alpha-1; D020032:Tyrphostins; C079836:tyrphostin 25; D017828:Rifabutin; C020754:herbimycin; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D016257:Fura-2; D009638:Norepinephrine