EDRF-mediated dilatation in the rat isolated perfused kidney: a microangiographic study.

摘要: 1 X-ray microangiographic techniques were used to study the influence of endothelium-derived relaxing factor (EDRF) on vasomotion in isolated, intact, buffer-perfused kidney rat. The main renal (R0), segmental (R1) and interlobar (R2) arteries (control diameters ca. 600, 400 300 μm respectively) studied quantitatively. 2 Inhibition basal EDRF activity by haemoglobin (1 μm) did not elevate perfusion pressure or constrict R0, R1 R2 control preparations, implying a low level spontaneous myogenic tone. In preparations preconstricted 0.3 methoxamine, caused further rise amplified constrictor responses while also inducing ‘paradoxical’ dilatation R0. 3 A spatially heterogeneous pattern diameter (constriction with minimal R0) was observed two concentrations methoxamine (0.3 3 μm). magnitude these was, however, smaller than even though it increased greater extent (88 mmHg cf. 24 mmHg). This behaviour indicates more pronounced constriction distal (which could be resolved quantitatively) methoxamine. 4 In contrast heterogeneity induced dilator action acetylcholine homogeneous: log IC50 values calculated from changes similar and, moreover, equivalent that corresponding alterations pressure. fall an approximately median effective concentration completely reversed haemoglobin, consistent involvement EDRF, although, reversal acetylcholine-induced observed. 5 The results are idea vessels can attenuate directionally reverse intrinsic proximal ‘feed’ producing overriding increase ‘upstream’ effect explains paradoxical R0 presence as compared failure R2.