Effect of somatostatin on rabbit isolated coronary arteries

Somatostatin analogues are capable of inhibiting vascular smooth muscle and endothelial cell proliferation. However, little is known about the effect of somatostatin on vascular responses in endothelium-denuded coronary arteries in vitro. The aim of this work was to determine whether or not somatostatin prevented the contractile response induced by 5-hydroxytryptamine and acetylcholine in endothelium-denuded rabbit coronary arteries. Somatostatin attenuated the contraction produced by 5-hydroxytryptamine in both proximal (PC) and distal coronary (DC) arteries (contraction induced by 10(-4) M 5-hydroxytryptamine was inhibited by 10(-6) M somatostatin by 90.8 +/- 11.0% (P < 0.001, n = 9) and by 46.2 +/- 14.0% (P < 0.05, n = 9) in DC and PC, respectively), but concentration-dependently decreased the contraction induced by U46619 (11alpha-epoxy-methanoprostaglandin F2alpha) only in PC arteries, suggesting that the response of PC and DC arteries to somatostatin were qualitatively different. Furthermore, we suggest that somatostatin may enhance acetylcholine-induced relaxation by combination of increasing endothelium-dependent relaxation (by a NO-dependent mechanism) and blocking contraction at the muscle level.