Vanadate-induced potentiation of smooth muscle contractility in the rat depolarized uterus.
The effect of ortho-vanadate on Ca(2+)-influx in the uterine smooth muscle was investigated. Orthovanadate (10-300 microM) gradually increased the muscular tone of rat isolated uterus bathed in a high K+ (30 mM)-low Ca2+ (0.15 mM) solution. This response was blocked by nifedipine (10 nM) and reproduced by BAY K 8644 (3-300 nM). Atropine and indomethacin were unable to block the effects induced by vanadate and BAY K 8644. Cumulative addition of CaCl2 to the tissue bathed in a depolarized solution without CaCl2 produced a graded tonic response that was potentiated by either vanadate (30 microM) or BAY K 8644 (30 nM), and inhibited by nifedipine. Neither vanadate (30 microM) nor BAY K 8644 (30 nM) modified the uterine tone of tissues immersed in the depolarizing solution without CaCl2. It is concluded that vanadate-induced contraction of rat uterine smooth muscle involves Ca(2+)-influx from the extracellular medium to the myometrial cell. Vanadate might act as a Ca(2+)-channel activator, similar to BAY K8644.
Ponce-Monter
H
H
Unidad de Investigación Médica en Farmacología, Hospital de Especialidades, Centro Médico Nacional Siglo XXI, Instituto Mexicano del Seguro Social, México, D.F.
Villaneuva
T
T
Ortega
B G
BG
Campos
M G
MG
D000818:Animals; D005260:Female; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014599:Uterus / Q000187:drug effects*; D014638:Vanadates / Q000494:pharmacology*
D014638:Vanadates