Role of Phosphatidylinositol Turnover in the Contraction of the Rat Aorta

The contraction of vascular smooth muscle in the rat aorta has been shown to be mediated exclusively by αl-adrenoceptors located on the cell membrane. These αl-adrenoceptors mediate vasoconstriction by stimulating both the influx of extracellular calcium through membrane calcium channels and the release of intracellular calcium stores (1,2). Recently, it has been hypothesized that full αl-adrenoceptor agonists can activate αl-adrenoceptors and stimulate both the influx of extracellular calcium and the release of intracellular calcium, whereas, partial αl-adrenoceptor agonists may only cause the influx of extracellular calcium (1,3).