ABSTRACT
In isolated b l o o d vessels, the respective cont r ibu t ion o f ni tr ic oxide, prostacycl in and E D H F to endothelium-dependent relaxation is usually addressed by drugs wh ich may affect the synthesis, release and/or effects o f these factors. Inhibitors o f ni t r ic oxide synthase or cycloxygenase are used to evaluate the role o f ni tr ic oxide and prosta cyc l in , respectively, and endothelium-dependent relaxations wh ich are resistant to inh ib i t ion o f these pathways are attributed to E D H F ( F é l é t o u and Vanhout te , 1999). In some arteries, E D H F - l i k e responses are inhibi ted by 18-/3 or 18-a-glycyrrhetinic acid (Taylor et al, 1998; Fu j imoto et al, 1999; F u k u t a et al, 1999; K a g o t a et al, 1999; Y a m a m o t o et al, 1999). A s these l ipophi l i c aglycones inhibi t gap junc t ionna l com municat ions (Dav idson et al, 1986; D a v i d s o n and Baumgarten, 1988; G u a n et al, 1996), hyperpolar iza t ion o f vascular smooth muscle cells in some b l o o d vessels may result f rom the electrical transfer and/or f rom the transfer o f diffusible factors v ia gap junct ions ( F é l é t o u and Vanhout te , 1999).
