Architecture of the rat nephron-arterial network: analysis with micro-computed tomography

Abstract

Among solid organs, the kidney's vascular network stands out, because each nephron has two distinct capillary structures in series and because tubuloglomerular feedback, one of the mechanisms responsible for blood flow autoregulation, is specific to renal tubules. Tubuloglomerular feedback and the myogenic mechanism, acting jointly, autoregulate single-nephron blood flow. Each generates a self-sustained periodic oscillation and an oscillating electrical signal that propagates upstream along arterioles. Similar electrical signals from other nephrons interact, allowing nephron synchronization. Experimental measurements show synchronization over fields of a few nephrons; simulations based on a simplified network structure that could obscure complex interactions predict more widespread synchronization. To permit more realistic simulations, we made a cast of blood vessels in a rat kidney, performed micro-computed tomography at 2.5-μm resolution, and recorded three-dimensional coordinates of arteries, afferent arterioles, and glomeruli. Nonterminal branches of arcuate arteries form treelike structures requiring two to six bifurcations to reach terminal branches at the tree tops. Terminal arterial structures were either paired branches at the tops of the arterial trees, from which 52.6% of all afferent arterioles originated, or unpaired arteries not at the tree tops, yielding the other 22.9%; the other 24.5% originated directly from nonterminal arteries. Afferent arterioles near the corticomedullary boundary were longer than those farther away, suggesting that juxtamedullary nephrons have longer afferent arterioles. The distance separating origins of pairs of afferent arterioles varied randomly. The results suggest an irregular-network tree structure with vascular nodes, where arteriolar activity and local blood pressure interact.

Blood flow synchronization in renal microcirculation - a high-resolution imaging study

“…It, however, does not mean that the observed clusters were limited to, at the most, 40 nephrons. When considering renal vascular topology, it is to be expected that within the 1.5x1.5µm field of view, we observe arterioles that arise from different non-terminal arteries 33 . Depending on the branching order, each of such arteries can branch into ten-several hundreds of nephrons, but only a small number of these nephrons will have arterioles reaching close enough to the surface to be segmented from LSCI images.…”

Rho kinase inhibitors reduce voltage-dependent Ca2+channel signaling in aortic and renal microvascular smooth muscle cells

“…The cortical tissue was pressed through a 180-m sieve and incubated in a digestion solution (0.016% collagenase D, 0.016% trypsin inhibitor, 0.016% dithiothreitol, and 0.016% albumin) at 36.5°C for 35-45 min. The preglomerular microvessels, consisting of interlobular arteries [also defined as cortical radial arteries (26)] and afferent arterioles, were carefully separated from tubular tissue under a stereomicroscope and transferred to a digestion solution containing 0.05% dithiothreitol, 0.14% papain, and 4% albumin dissolved in a low-Ca 2ϩ (50 M) PSS at 36.5°C. After a 15-to 25-min incubation period, the mixture was centrifuged (900 g for 2-3 min) to pellet the dispersed cells.…”

Three-dimensional morphometric analysis of the renal vasculature

“…Sled et al observed a high degree of similarity in the distribution of vessel diameters within mouse kidneys based on micro-CT images (31). Marsh et al scanned polymer cast of a rat renal vasculature using low-and high-resolution micro-CT imaging (23). They measured the segmental lengths of arteries and afferent arterioles and distances between arteriolar pairs to study vascular organizational patterns in the arterial-nephron network.…”