Oxytocin-induced phosphorylation of myosin light chain is mediated by extracellular calcium influx in pregnant rat myometrium.
Studies of oxytocin-induced phosphorylation of myosin light chain (MLC), resulting in myometrial contraction, suggest that extracellular Ca(2+) influx is involved in its signal transduction. To explore the possibility that intracellular Ca(2+) mobilization by oxytocin may also contribute to MLC phosphorylation, we investigated the relative contributions of these Ca(2+) sources to oxytocin signal transduction in myometrium of pregnant rat. In pregnant rat myometrium, oxytocin-induced Ca(2+) influx occurs via an L-type voltage-dependent Ca(2+) channel. Treatment with verapamil, an antagonist specific for these channels, significantly diminished MLC phosphorylation observed in response to oxytocin administration without affecting the release of Ca(2+) from intracellular Ca(2+) stores. Furthermore, oxytocin-induced MLC phosphorylation was not observed when extracellular Ca(2+) was not present. Our results clearly indicate that extracellular Ca(2+) influx, rather than release from Ca(2+) storage sites, is essential for oxytocin-induced MLC phosphorylation.
Shojo
H
H
Department of Forensic Science, Saga Medical School, 5-1-1 Nabeshima, Saga 849-8501, Japan.
Kaneko
Y
Y
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D009215:Myometrium / Q000378:metabolism*; D018994:Myosin Light Chains / Q000187:drug effects / Q000378:metabolism*; D010121:Oxytocin / Q000378:metabolism / Q000494:pharmacology*; D010766:Phosphorylation; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar
D018994:Myosin Light Chains; D010121:Oxytocin; D002118:Calcium