Role of the endothelium in the relaxation induced by propofol and thiopental in isolated arteries from man.

Induction of anaesthesia with intravenous propofol and thiopental is often accompanied by hypotension. This study evaluates whether propofol and thiopental induce relaxation of isolated arteries from man and whether this effect is modulated by the endothelium. Mesenteric artery rings (with and without endothelium) from 12 patients were placed in organ baths and precontracted with phenylephrine before addition of propofol (10(-3) M) or thiopental (10(-3) M). Relaxation induced by propofol and thiopental was evaluated for rings with intact endothelium in the presence of the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME; 10(-4) M) or the cyclooxygenase inhibitor indomethacin (10(-5) M). The vasodilator effect of propofol was similar for intact and denuded endothelium rings whereas the relaxation induced by thiopental was significantly attenuated in denuded-rings. In intact endothelium rings, L-NAME and indomethacin caused marked inhibition of the relaxation induced by thiopental, but not that induced by propofol. These results suggest that propofol induces endothelium-independent relaxation of isolated mesenteric arteries in man, whereas thiopental causes endothelium-dependent relaxation mediated by nitric oxide and prostaglandins.