The α1-agonist phenylephrine inhibits voltage-gated Ca2+-channels in vascular smooth muscle cells of rabbit ear artery
✍ Scribed by I. Declerck; B. Himpens; G. Droogmans; R. Casteels
- Publisher
- Springer
- Year
- 1990
- Tongue
- English
- Weight
- 369 KB
- Volume
- 417
- Category
- Article
- ISSN
- 0031-6768
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✦ Synopsis
The effects of the alpha 1-agonist phenylephrine on the voltage-gated Ca2(+)-entry in vascular smooth muscle cells has been studied by measuring the agonist-induced changes of [Ca2+]i in K(+)-depolarized tissues. These changes have been estimated from the changes in fluorescence of the Ca2(+)-indicator fura-2, or have been assessed from the changes in 86Rb-efflux rate through Ca2(+)-activated K(+)-channels. Phenylephrine increases the force development in K(+)-depolarized tissues, but reduces [Ca2+]i and inhibits the 86Rb-efflux rate. However, in the presence of the Ca2(+)-entry blocker verapamil, phenylephrine increases both force development and [Ca2+]i. It is concluded that phenylephrine inhibits voltage-gated Ca2(+)-channels, and also induces an influx of calcium by activating a verapamil-insensitive pathway.