PREPARATION AND APPLICATION OF AN ISOLATED SUPERIOR MESENTERIC ARTERIAL VASCULAR PREPARATION

Our laboratory developed an isolated perfused superior mesenteric arte rial vascular bed preparation to study and correlate vascular smooth-m uscle mechanics with associated biochemical events. This preparation p rovides consistent dose-dependent contractile responses, contains most of the superior mesenteric artery as well as first-, second-, and thi rd-generation arterioles, and has been used for concurrent functional and biochemical analysis of vascular smooth muscle. Preparations isola ted from Sprague-Dawley rats produced rapid, dose-related vasoconstric tor responses to norepinephrine (NE) and KCl, while appearing to be un responsive to periarterial nerve stimulation. Endothelial relaxations to bolus doses of acetylcholine (ACh) in the presence of a constant in fusion of NE (10 mu M) were limited, producing reductions of perfusion pressures of <25%. Receptor-binding studies conducted to evaluate al- adrenoceptor subtypes revealed high- and low-affinity binding sites co mposing 91 and 9% of the overall population, respectively. A 60-s time course for contractile response and inositol 1,4,5-triphosphate (IP3) production revealed a significant but transient increase of IP3 that paralleled the contractile response generated by using bolus injection s of NE (30 mu g). This preparation offers the capacity to conduct per fusion studies investigating vasoconstrictor responses, as well as bio chemical studies including receptor-binding and second-messenger assay s in the same tissue.