Abstract
The role of catecholamines in the distribution of intrarenal blood flow and in single-nephron glomerular filtration rate (SNGFR) was evaluated in anesthetized Wistar rats by the Hanssen technique. Epinephrine (EPI) and norepinephrine (NOR) were infused to produce elevations of 20-30 mmHg in mean arterial pressure. Superficial and juxtamedullary nephron perfusion and filtration were determined by the presence of Prussian blue dye. In the control group, 100% of the nephrons presented a homogeneous pattern of perfusion and filtration. In contrast, a heterogeneous distribution of the dye was found even in the larger arteries (arciform and radial), indicating variable perfusion and filtration in both superficial and juxtamedullary nephrons. The effects of EPI and NOR were also evaluated in the superficial cortex by the micropuncture technique in two additional groups of Munich-Wistar rats. Mean SNGFR was 27% and 54% lower in the EPI- and NOR-treated groups, respectively. No change in mean intraglomerular hydraulic pressure was observed after EPI or NOR infusion in spite of a highly scattered pattern, indicating an important variability in perfusion along the superficial cortex, and/or different sensitivity of the pre- and post-glomerular arterioles. The present data suggest that EPI and NOR may affect intrarenal hemodynamics by modifying perfusion and filtration in both superficial and juxtamedullary glomeruli and not by shifting blood flow from superficial to juxtamedullary nephrons. The heterogeneous pattern of perfusion was a consequence of differential vasoconstriction along the intrarenal arteries, probably due to different density and/or sensitivity of the adrenergic receptor subtypes present in the intrarenal vascular tree.
Highlights
The distribution of intrarenal blood flow among the different nephron populations may play an important physiological and pathophysiological role
The kidney presents a high concentration of adrenergic receptors [1,2,3,4] and, based on pharmacological and molecular techniques, the expression of the α- and ß-adrenergic receptor subtypes has been observed in the different regions of the nephron [5,6,7,8]
We have reinvestigated the question of the distribution of blood flow in superficial and juxtamedullary nephron populations during renal vasoconstriction induced by epinephrine (EPI) and norepinephrine (NOR) using the Hanssen technique
Summary
The distribution of intrarenal blood flow among the different nephron populations may play an important physiological and pathophysiological role. These differences are mediated in part by sympathetic neural control since the renal vasculature and other parts of the nephron receive extensive noradrenergic innervation [1]. Studies evaluating intrarenal blood flow distribution under different conditions and by different techniques have produced conflicting results [11,12,13,14,15,16]. We have reinvestigated the question of the distribution of blood flow in superficial and juxtamedullary nephron populations during renal vasoconstriction induced by epinephrine (EPI) and norepinephrine (NOR) using the Hanssen technique. The functional behavior of the superficial nephrons was investigated by micropuncture
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Schedule a callMore From: Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas
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