Vanadate increases cytosolic free calcium in rat aortic smooth muscle cells.
Although several studies have shown that vanadate evokes vasoconstriction whether it elevates cytosolic free calcium, [Ca2+]i, in vascular smooth muscle (VSM) cells has not been investigated. The present study shows that acute additions of low concentrations of vanadate (10-200 microM) to cultured aortic smooth muscle cells (ASMC) produced a rapid and a concentration-dependent increase in [Ca2+]i with an EC50 (mean +/- SEM) value of 42 +/- 11 microM. Inclusion of vanadate (200 microM) led to a significant increase (p < 0.05) in the peak [Ca2+]i level to 190 +/- 23 nM from a basal level of 102 +/- 2 nM. At concentrations > 200 microM, vanadate caused quenching of fura-2 fluorescence. For example, addition of 1 mM vanadate led to an apparent decrease in fluorescence by about 50% (due to a quenching effect), followed by a transient rise. H2O2, which is used in the preparation of peroxide forms of vanadate, pervanadate (PV), also produced a rise in [Ca2+]i. These data suggest that vanadate promotes vascular tone by elevating [Ca2+]i in ASMC. However, [Ca2+]i measurements made with higher concentrations of vanadate and PV, using the fura-2 method, must be interpreted with caution.
Sandirasegarane
L
L
Department of Pharmacology, College of Medicine, University of Saskatchewan, Saskatoon, Canada.
Gopalakrishnan
V
V
D000818:Animals; D001011:Aorta / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005453:Fluorescence; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014638:Vanadates / Q000494:pharmacology*
D014638:Vanadates; D006861:Hydrogen Peroxide; D002118:Calcium