Effect of somatostatin on resistance and on capacitance rabbit isolated arteries

The effects of somatostatin, a tetradecapeptide isolated from hypothalamus extracts, were studied on the vascular reactivity of aorta and mesenteric a rteries isolated from rabbits. We also investigated whether or not Ca2+ mov ements were implicated in these effects. Rabbit aorta and mesenteric (fifth branch) arteries were isolated, cleaned off, and mounted in an organ bath containing Godfraind solution or physiological saline solution (PSS), respe ctively. Somatostatin (10(-8)-10(-4) M) produced a concentration-dependent inhibition of the contractile responses induced by high K+ (80 mM) or norad renaline (10(-6) M in aorta or 10(-4) M in mesenteric arteries) in both art eries studied. The inhibitory effect of somatostatin was greater in mesente ric resistance vessels (IC50 3.1 +/- 2.3 x 10(-5) M, and 5.2 +/- 4.8 x 10(- 8) M with KCl and noradrenaline, respectively). Contractile responses produ ced by the addition of Ca2+ (1-5 mM) to Ca2+-free high K+ solution were als o concentration dependently inhibited by somatostatin in aorta. Furthermore , somatostatin decreased noradrenaline-induced contraction attributed to in tracellular Ca2+ release in aorta, and inhibited Ca-45(2+) uptake stimulate d by high KC or by noradrenaline. However. it did not modify Ca-45(2+) upta ke in resting mesenteric resistance arteries. Taken together, these results suggest that somatostatin exerts an inhibitory effect on vascular contract ions induced by some stimulating agents in different arteries isolated from rabbits, being more potent in mesenteric arteries. (C) 2000 Elsevier Scien ce B.V. All rights reserved.