So. Mikalsen et O. Kaalhus, A CHARACTERIZATION OF PERVANADATE, AN INDUCER OF CELLULAR TYROSINE PHOSPHORYLATION AND INHIBITOR OF GAP JUNCTIONAL INTERCELLULAR COMMUNICATION, Biochimica et biophysica acta (G). General subjects, 1290(3), 1996, pp. 308-318
Gap junctional intercellular communication (GJIC), phosphorylation sta
tus of the gap junction protein, connexin43 (Cx43), and cellular tyros
ine phosphorylation in Syrian hamster embryo cells have been employed
for a biological characterization of pervanadate (a mixture of H2O2 an
d vanadate), In addition, electron paramagnetic resonance (EPR) spectr
oscopy was used to follow the appearance and disappearance of vanadyl
(V(IV)), It has previously been suggested that pervanadate is vanadyl
hydroperoxide (V-(4+)OOH), This assumption was tested by using mixture
s with different molar ratios of H2O2 and orthovanadate, metavanadate
or vanadyl sulfate. The maximal biological activity of the mixtures we
re found at a molar ratio of 2:1 (H2O2:orthovanadate or metavanadate)
or 2.5:1 (H2O2:alkaline vanadyl sulfate). No V(TV) EPR spectrum appear
ed upon mixing orthovanadate or metavanadate and H2O2. The V(IV) EPR s
pectrum disappeared when vanadyl sulfate was incubated with H2O2 in a
0.5:1 molar ratio (H2O2:alkaline vanadyl sulfate), Spectrophotometrica
lly, a V(V)-like peak at 265 nm had its optimum at this ratio. These r
esults are consistent with pervanadate being diperoxovanadate. The ind
ividual compounds were prominently less active than the per-compound m
ixtures in affecting the biological parameters, The decreases in GJIC
showed a concentration-dependent correlation with the onset of the alt
erations of the Cx43 band pattern and the amount of phosphotyrosine in
cellular proteins, but the correlation was not absolute. All the stud
ied biological parameters were reversible, also under continuous expos
ure to pervanadate.