PubMed · 4085239
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H J Schubert, E Prater, M Sell. 1985. Patch testing with primin in white petrolatum.. https://doi.org/10.1111/j.1600-0536.1985.tb02576.x
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Specific inhibitors of the endoplasmic-reticulum Ca2+ pump will deplete intracellular stores and are therefore useful to study the role of store depletion on plasma-membrane Ca2+ permeability. We now report that the Ca(2+)-pump inhibitor 2,5-di-(tert-butyl)-1,4-benzohydroquinone (tBuBHQ) reduces the passive Ca2+ leak from the internal stores in permeabilized A7r5 vascular smooth-muscle cells. This aspecific effect occurred at concentrations that are normally used to empty the stores in intact cells. Cyclopiazonic acid exerted a similar, although less pronounced effect, while thapsigargin did not affect the passive Ca2+ leak. The inositol 1,4,5-trisphosphate-mediated Ca2+ release was not affected. tBuBHQ and cyclopiazonic acid cannot therefore be used as specific tools to probe the mechanism of receptor-mediated Ca2+ entry.
Interferon-gamma (IFN gamma) is a potent immunomodulatory cytokine. However, the early mechanisms which mediate the pleiotropic effects of IFN gamma on different cells are as yet poorly understood. Therefore, we tested the role of tyrosine phosphorylation in signalling induced by IFN gamma. IFN gamma was found to induce rapid tyrosine phosphorylation of several proteins in HL-60 cells. This effect was detectable by 2 min, reached a maximum by about 4-16 min and thereafter declined. Tyrosine phosphorylation was dependent on receptor occupation and was maximally stimulated by 10 ng/ml IFN gamma. Treatment of HL-60 cells with the tyrosine kinase inhibitors, genistein and herbimycin A, inhibited both IFN gamma-stimulated tyrosine phosphorylation and IFN gamma-induced Fc receptor expression. Thus, increased tyrosine phosphorylation appears to be an obligatory early and proximal signal mediating at least some of the later cellular responses induced by IFN gamma in HL-60 cells.
To study the effect of chelation of iron ions by quinones on the generation of OH radicals in biological redox systems, we have synthesized quinones that can form complexes with Fe(III) ions: 2-phenyl-4-(butylamino)naphtho[2,3-h]quinoline-7,12-dione (Qbc) and 2-phenyl-4-(octylamino)naphtho[2,3-h]quinoline-7,12-dione (Qoc). A quinone with a similar structure without chelating group was synthesized as a control sample: 2-phenyl-5-nitronaphtho[2,3-g]indole-6,11-dione (Qn). Using optical spectroscopy, we determined the stability constant of Qbc with Fe(III) [Ks = (7 +/- 1) x 10(18) M-3] and the stoichiometry of the complex Fe(Qbc)3 in chloroform solutions. One-electron reduction potentials of Qbc, Qn, and adriamycin in dimethyl sulfoxide were measured by cyclic voltammetry. In the presence of Fe(III) the one-electron reduction potentials shifted toward positive values by 0.16 and 0.1 V for Qbc and adriamycin, respectively. Using the spin trap 5,5'-dimethyl-1-pyroline N-oxide (DMPO) and EPR, it was found that Qbc in the Fe(III) complex stimulated the formation of OH radicals in the enzymatic system consisting of NADPH and NADPH-cytochrome P-450 reductase more efficiently than adriamycin and quinone Qn. This is indicated by the absence of a lag period in the spin adduct appearance for Qbc and by a significantly higher rate of the spin adduct production, as well as by a larger absolute concentration of the spin adduct obtained for Qbc in comparison with Qn in the presence of Fe(III).(ABSTRACT TRUNCATED AT 250 WORDS)