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.

Endothelin-induced long-lasting mesenteric vasoconstriction: a hypothetical mechanism of non-occlusive intestinal infarction.

The in vivo mesenteric vascular effect of the novel, endothelium-derived endogenous polypeptide, endothelin-1 (ET-1) was examined in experiments performed on pentobarbital-anesthetized dogs. Blood supply to a segment of the small bowel was measured simultaneously with an electromagnetic flow probe and computer-assisted thermography which senses flow-dependent infrared irradiation. It was found that close mesenteric arterial injections of ET-1 produced long-lasting flow decreases of considerable magnitude: the single dose of 1 nmol reduced blood flow by nearly 90 percent, and even the minimal single amount of 1 pmol produced statistically significant vasoconstriction. The thermographic analysis proved the homogenous character of these reactions. Unlike vascular responses elicited by most of the known vasoconstrictive agents, the ET-1-induced spastic effects were maintained without a continuous exposure (drug infusion). All features that characterize the spastic ET-1 action qualify the peptide for a hypothetical candidate of mediating the nonocclusive mesenteric ischemic syndrome.

[Biochemical serum parameter changes during and after autologous small intestine transplantation in animal experiments. I. Intra- and immediate postoperative period]. / Biochemische Serumparameterveränderungen während und nach autologer Dünndarmtrans-plantation im Tierexperiment. I. Mitteilung: Intra- und unmittelbar postoperative Phase.

Biochemical parameters sodium, potassium, lactate, alkaline phosphatase, ASAT, and ALAT were examined at the beginning of the operation, before, and 0, 2, 4, 6 hours after implantation of a small bowel autograft in an autologous model of intestinal transplantation in dogs. By the way of these early biochemical studies we have got information about metabolic situation during organ transplantation, efficiency of preservation and vitality of the graft. Using the given method safe preservation of small bowel can be guaranteed. Postoperatively only little changes of laboratory parameters occur.

Factors influencing the vascular action of dopamine in the canine mesenteric bed.

The effect of dopamine on the mesenteric arterial bed was investigated in dogs anaesthetized with pentobarbital sodium. The vascular responses to dopamine in a branch of the superior mesenteric artery supplying a segment of the small intestine were measured with a flowmeter probe and visualized by infrared telethermography or, in a separate series of dogs, were obtained by the direct determination of arterial resistance--changes during perfusion with constant flow. It was found that the mesenteric action of dopamine (given i.v. in the submaximal dose of 16 micrograms.kg-1.min-1 or intraarterially up to a dose of 40 micrograms.min-1) is primarily mediated via dopaminergic vasodilator and a alpha-adrenergic vasoconstrictor receptors, the net result of this competition usually being moderate vasodilation under natural conditions. The contribution of beta-adrenergic vasodilation to the mesenteric dopamine action is minimal as evidenced by beta-blockade with oxprenolol. By blocking the alpha-component with phentolamine (1.0 mg.kg-1) an almost threefold increase of the vasodilation was obtained in resistance. Because of the concomitant reversal of the systemic hypertensive dopamine action to hypotension, the net flow increase remained essentially unchanged. It was concluded that unless the degree of alpha-stimulation is restrained and proper control of blood pressure is ensured, it is not possible to recommend that dopamine be used in the therapy of mesenteric vascular disorders.

Motility, haemodynamics and responsibility to vasoactive agents after revascularization of autotransplanted small intestine segments in the dog.

Functional and haemodynamic changes occurring after revascularization of an autotransplanted small intestine segment were studied in acute experiments performed in 10 dogs under pentobarbital anaesthesia. Intestinal motility and mesenteric blood flow of the segment were measured with intraluminal pressurized balloon and electromagnetic flowmeter, respectively. The time-course of observations was divided, according to the findings, into three main periods (phases 1 to 3). In the initial phase (1) the bowel exhibited very slight spontaneous motility which was found to increase moderately but significantly after denervation and isolation of the graft still left in situ before transplantation (phase 2). After declamping of anastomoses of the retransplanted graft (which was protected by cooling to 4 degrees C after being removed from the body) a short period (approximately 2 min) of reactive hyperaemic flow increase was observed in association of vigorous bowel movements lasting for a more prolonged (approximately 15 min) period of time (phase 3a and 3b). Reactivity of the retransplanted vasculature as compared to the denervated control revealed a marked relative shift in adrenergic balance, tested by dopamine, to the vasoconstrictor range, but it showed no change in responses to general haemodynamic or haemorheologic interventions, tested by veratrine and pentoxifylline, respectively. However, the basic levels of blood supply (controlled also by thermography) and systemic blood pressure remained unaltered after transplantation. Regarding the critical role of functional changes immediately after transplantation in determining the survival of bowel grafts, these observations may contribute to a more effective monitoring of surgical interventions.