APStracts 3:0234H, 1996.

Nitric oxide dependent opposite effects of somatostatin on arterial and venous caliber in situ. Szentiv[acute]anyi, N[acute]aty[acute]as, Gy[diaeresis]orgy L. N[acute]adasy, L[acute]aszl[acute]o D[acute]ezsi, G[acute]eza M[acute]ozes, Tivadar Tulassay, E. Monos. Clinical Research Department - 2nd Institute of Physiology, 2nd Institute of Pathology, and 1st Clinic of Pediatrics, Semmelweis University of Medicine, Budapest, Hungary

APStracts 3:0234H, 1996.

The vascular effects of somatostatin (ST) and its mechanism of action are not well understood. In the present study, we investigated the direct effects of ST on the vascular tone of rat saphenous artery and vein using video-microangiometry in situ. ST was administered either in superfusion or in infusion. We found opposite effects in arteries and veins: ST (10-12-10-7 mol/l) dilated the artery (outer diameter increased from 533+/-28 to 600+/-29 [mu]m, administered in superfusion) and contracted the vein (from 709+/-26 to 640+/-26 [mu]m and from 775+/-30 to 708+/-60 [mu]m in superfusion and in infusion, respectively). These effects of ST were completely abolished after deendothelisation (maintained an air bolus for 6 minutes in the vessel lumen), and by local infusion of LNNA (10-4 mol/l), a nitric oxide synthesis inhibitor. An NO-dependent basal vasodilator tone in the rat saphenous vein, responsible for 10.9+/-0.3 % of the total vessel diameter was found. After ST administration the venous diameter reduction was similar to that of measured after deendothelisation, or LNNA. We conclude, that ST in situ induces nitric oxide release from endothelial cells of rat saphenous artery causing vasodilation, while, in contrast, it inhibits the basal nitric oxide-dependent vasodilator tone of the saphenous vein inducing vasocontstriction.

Received 4 December 1995; accepted in final form 20 May 1996.
APS Manuscript Number H1127-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 17 June 96