Decrease In Mesenteric Flow Research Articles

The effects of insulin on mesenteric blood flow in anaesthetized pigs.

Infusion of insulin in anaesthetized pigs has been shown to cause an increase in renal blood flow and a decrease in coronary blood flow, which were the net result of a vasoconstriction involving sympathetic alpha-adrenoceptor-mediated mechanisms and of a local vasodilatation involving the endothelial release of nitric oxide. In the present study, the effect of insulin on superior mesenteric blood flow was examined in pentobarbitone-anaesthetized pigs at constant heart rate, aortic blood pressure, left ventricular contractility and blood levels of glucose and potassium. In 10 pigs, infusion of 0.004 IU kg(-1) min(-1) of insulin increased mesenteric flow. In five of these pigs, intravenous phentolamine enhanced the increase in mesenteric flow elicited by insulin, a response which was abolished by the subsequent injection of N(omega)-nitro-L-arginine methyl ester (L-NAME) into the mesenteric artery. In the remaining five pigs, infusion of insulin after intramesenteric injection of L-NAME caused a decrease in mesenteric flow. This response was abolished by the subsequent intravenous administration of phentolamine. The present study showed that infusion of insulin in anaesthetized pigs primarily caused a mesenteric vasodilatation, which was the net result of two opposite effects, namely a predominant vasodilatation mediated by the endothelial release of nitric oxide and a sympathetic vasoconstrictor mechanism mediated by alpha-adrenoceptors.

The effect of distension of the stomach on peripheral blood flow in anaesthetized pigs.

The present study was undertaken in anaesthetized pigs to determine the primary reflex effects of gastric distension on the peripheral circulation. Changes in blood flow in the splenic, superior mesenteric, left renal and left external iliac arteries were assessed using electromagnetic flowmeters during distension of a balloon in the stomach, performed at constant aortic blood pressure and heart rate, with 0.6 l of Ringer solution (mean gastric transmural pressure of about 12 mmHg). In fourteen pigs, a decrease in splenic, renal and iliac flows and variable changes in mesenteric flow were obtained. A decrease in mesenteric flow and more marked decreases in the other flows occurred in response to the distension after the administration of propranolol or butoxamine. In five pigs, the vasoconstrictive responses were graded by step increments in gastric distending volume from 0.4 to 0.8 l. The above responses were abolished by the administration of phentolamine (eight pigs) and by bilateral cervical vagotomy (six pigs). The results showed that innocuous distension of the stomach in anaesthetized pigs reflexly caused vasoconstriction in the splenic, renal and iliac vascular beds; vasoconstriction also occurred in the mesenteric vascular bed but only after beta-blockade. These reflex responses were mediated by sympathetic mechanisms which involved both alpha and beta vascular adrenoceptors and their afferent limb was in the vagal nerves.

Vasoactivity and immunoreactivity of fish tachykinins in the vascular system of the spiny dogfish.

Tachykinin control of gut blood flow (measured by pulsed Doppler technique), dorsal aortic pressure, and heart rate were studied in unrestrained spiny dogfish Squalus acanthias injected with the elasmobranch tachykinins scyliorhinin I and II (SCY I and SCY II), the trout tachykinins substance P (SP), and neurokinin A (NKA). Effects on somatic vasculature were measured by in vitro perfusion of the isolated tail. SCY I and trout SP produced hypotension due to a general vasodilation. This caused a transient increase in mesenteric blood flow and a prolonged increase in celiac blood flow. SCY II caused an initial hypertension induced by a general vasoconstriction, followed eventually by an elevated flow in both gut arteries due to dilation of the vascular beds. Trout NKA evoked a short-lasting increase in celiac blood flow due to a decrease in vascular resistance, a late decrease in mesenteric flow due to vasoconstriction, and no effect on the somatic vasculature. None of the peptides affected heart rate. The study demonstrates a significant vasoactive function of fish tachykinins in the vascular system of an elasmobranch species and, in addition, the occurrence of tachykinin receptor subtypes. Immunohistochemistry revealed a NKA/SCY II-like peptide in nerve fibers innervating many vessels, including the celiac and the mesenteric arteries, the gastrointestinal canal, and the heart.