ET(A) receptor blockade protects the small intestine against ischaemia/reperfusion injury in dogs via an enhancement of antioxidant defences

The aim of the present study was to determine whether the ET(A) receptor antagonist LU135252 can protect the mesenterium against ischaemia/reperfusion (I/R) damage. Direct occlusion of the superior mesenteric artery was performed for 30 min in two groups of dogs. Declamping was followed by 90 min of reperfusion. Mesenteric release of ET-1 was studied in series 1 (n=6). In series 2, 5 min before cross-clamping, the treated group (n=7) received an intravenous bolus of LU135252 (5 mg/kg), whereas the control group (n=6) was given vehicle. Mean arterial blood pressure and mesenteric blood flow were recorded. Mesenteric venous and systemic arterial serum lactate and glucose, plasma creatine kinase and free radical concentrations were determined at 15 min intervals. Ischaemia for 30 min induced a significant increase (P<0.05) in mesenteric ET-1 release (1594+/-526 pg/min, compared with 343+/-258 pg/min at baseline), which had returned to baseline after 20 min of reperfusion. LU135252 administration significantly decreased mesenteric blood flow during ischaemia (204+/-23%) compared with controls (320+/-34%, P<0.05). In contrast, mesenteric blood flow was higher in the treated group (120+/-19% compared with 82+/-7%; P<0.05) after 90 min of reperfusion. Mesenteric lactate production was reduced by ET(A) antagonist administration under ischaemia (0.77+/-0.02 mmol/l) compared with controls (1.36+/-0.04 mmol/l; P<0.01). Lower levels of venous creatine kinase were present in the treated group during ischaemia as well as after reperfusion (120+/-7% compared with 150+/-16%; P<0.01). Administration of LU135252 also improved the total scavenger capacity of the mesenteric bed during ischaemia [(15.9+/-3.9)x10(6) compared with (6.4+/-3.6)x10(6) relative light units; P<0.05] and early reperfusion [(8.7+/-3.1)x10(6) compared with (1.1+/-2.9)x10(6) relative light units]. Thus ET-1 is involved in I/R-induced disturbances in the intestine. LU135252 seems to counteract these changes, in part by increasing the antioxidant capacity of the mesenterium.

Direct renovascular effect of somatostatin in the dog

Recently, effects of somatostatin on the renal function have been described and the vasoactive properties of the peptide were proposed to contribute to this action. However, the available data on its effect in the renal vascular bed are very controversial. Therefore, we investigated the effect of local intaarterial somatostatin boluses in a wide range of doses (5 x 10(-11) - 5 x 10(-5) g) on the renal blood flow (RBF) in anesthetized dogs. RBF was measured by an electromagnetic flow probe. Somatostatin did not influence blood pressure or heart rate. RBF exhibited a significant, dose-dependent fall (ranging from 11.6 +/- 11.9% to 31.9 +/- 17.3%), with a threshold at a dose of 5 x 10(-10) g. These results offer conclusive evidence for the contribution of somatostatin-induced direct renal vasoconstriction to its renal effects, in addition to the demonstrated modulation of other vasoactive systems and tubular functions.