A CHARACTERIZATION OF PERMOLYBDATE AND ITS EFFECT ON CELLULAR TYROSINE PHOSPHORYLATION, GAP JUNCTIONAL INTERCELLULAR COMMUNICATION AND PHOSPHORYLATION STATUS OF THE GAP JUNCTION PROTEIN, CONNEXIN43

Biological and analytical characterizations of permolybdate (a mixture of H2O2 and molybdate) were done. Molybdate (10 mM) and molybdenum(V) chloride (3 mM) did not affect gap junctional intercellular communica tion (GJIC), phosphorylation status of connexin43 (Cx43) or cellular t yrosine phosphorylation in early passage hamster embryonic cells (main ly fibroblast-like), High concentrations of H2O2 (3-10 mM) affected so me of the parameters. Acidified permolybdate was clearly more stable t han the unadjusted permolybdate. The maximum biological potency of aci dified permolybdate was found at a molar ratio of 2:1 (H2O2:molybdate) . The mixtures of molybdenum(V) chloride and H2O2 gave a maximum effec t at 4:1 molar ratio (H2O2:molybdenum(V)). This can be explained by de composition of H2O2 and by the generation of less biologically active compounds. Spectrophotometric analyses of the mixtures corroborated th e biological results. The Mo(V) electron spin resonance spectrum disap peared upon addition of H2O2 to Mo(V) solutions, and no spectrum appea red when H2O2 was mixed with Mo(VI). Thus, permolybdate is probably di peroxomolybdate, a Mo(VI) compound. Regardless of the parent metal sal t, the H2O2/metal salt mixtures showed concentration-dependent biphasi c responses with an initial decrease in GJIC followed by an increase. A dissociation between alteration in Cx43 phosphorylation status and G JIC was obtained under certain conditions. The biological activities o f permolybdate were only partially mimicked by phenylarsine oxide, an alternative protein tyrosine phosphatase inhibitor.