Effects of activation of vasopressin-V1-receptors on regional kidney blood flow and glomerular arteriole diameters

Correia, Anabela G.; Denton, Kate M.; Evans, Roger G.

doi:10.1097/00004872-200103001-00019

Cited by 22 publications

(18 citation statements)

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“…The model assumes that flow rates and solute concentrations of the descending limbs and DVR are known a priori and CD fluid composition is computed from ascending limb flows at the cortico-medullary boundary. It is known that vasopressin reduces blood flow in DVR by affecting the contractility of pericytes (5,42,60). To understand how the action of the hormone on vascular receptors impacts medullary blood flow and the model's concentrating capability, we varied base-case cortico-medullary DVR boundary flow rate of 8 nl/min per DVR by Ϯ10 and Ϯ20%; DVR boundary solute concentrations were kept at the base-case values.…”

Section: Resultsmentioning

confidence: 99%

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Urine concentrating mechanism: impact of vascular and tubular architecture and a proposed descending limb urea-Na⁺cotransporter

Layton

Dantzler

Pannabecker

2012

American Journal of Physiology-Renal Physiology

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Layton AT, Dantzler WH, Pannabecker TL. Urine concentrating mechanism: impact of vascular and tubular architecture and a proposed descending limb urea-Na ϩ cotransporter. Am J Physiol Renal Physiol 302: F591-F605, 2012. First published November 16, 2011 doi:10.1152/ajprenal.00263.2011.-We extended a region-based mathematical model of the renal medulla of the rat kidney, previously developed by us, to represent new anatomic findings on the vascular architecture in the rat inner medulla (IM). In the outer medulla (OM), tubules and vessels are organized around tightly packed vascular bundles; in the IM, the organization is centered around collecting duct clusters. In particular, the model represents the separation of descending vasa recta from the descending limbs of loops of Henle, and the model represents a papillary segment of the descending thin limb that is water impermeable and highly urea permeable. Model results suggest that, despite the compartmentalization of IM blood flow, IM interstitial fluid composition is substantially more homogeneous compared with OM. We used the model to study medullary blood flow in antidiuresis and the effects of vascular countercurrent exchange. We also hypothesize that the terminal aquaporin-1 null segment of the long descending thin limbs may express a urea-Na ϩ or urea-Cl Ϫ cotransporter. As urea diffuses from the urea-rich papillary interstitium into the descending thin limb luminal fluid, NaCl is secreted via the cotransporter against its concentration gradient. That NaCl is then reabsorbed near the loop bend, raising the interstitial fluid osmolality and promoting water reabsorption from the IM collecting ducts. Indeed, the model predicts that the presence of the urea-Na ϩ or urea-Cl Ϫ cotransporter facilitates the cycling of NaCl within the IM and yields a loop-bend fluid composition consistent with experimental data. kidney; anti-diuresis; NaCl transport; urea transport WHEN DEPRIVED OF WATER, the mammalian kidney can produce a cortico-papillary osmotic gradient that gives rise to a urine that is much more concentrated than blood plasma. It is generally believed that the inner medullary (IM) osmotic gradient, like the outer medullary (OM) gradient, is generated by means of segment-specific interactions among the renal tubules and vessels. Washout of the gradient is prevented, in part, by means of vascular countercurrent exchange. However, the precise mechanism by which an osmolality gradient (especially the NaCl gradient; Ref. 27) is generated along the cortico-medullary axis of the IM remains controversial (32, 54).Recent anatomic findings have revealed in the IM of the rat kidney a highly structured organization of tubules and vessels. In the initial IM, vascular bundles exist as distinct entities consisting of a number of descending vasa recta (DVR) intermixed with a somewhat larger number of ascending vasa recta (AVR; Ref. 69). These vasa recta are the primary conduits for blood flow into and out of the IM and engage in countercurrent exchange of fluid and solutes....

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Section: Resultsmentioning

confidence: 99%

“…[5][6][7], where the fractions ␣LDV,R5, ␣LDV,R6, and ␣LDV,R7 denote the fractions of the blood source directed into R5, R6, and R7, respectively. QR7,R5 and QR7,R6 represent the capillary flows from R7, where the CD resides, into R5 and R6.…”

Section: Mathematical Modelmentioning

confidence: 99%

Urine concentrating mechanism: impact of vascular and tubular architecture and a proposed descending limb urea-Na⁺cotransporter

Layton

Dantzler

Pannabecker

2012

American Journal of Physiology-Renal Physiology

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“…10,11,24,25 Anesthesia was induced with sodium pentobarbital (90 to 150 mg plus 30 to 50 mg/h). Artificial ventilation and infusion of maintenance solutions then continued for the entire experiment.…”

Section: Surgical Proceduresmentioning

confidence: 99%

“…Artificial ventilation and infusion of maintenance solutions then continued for the entire experiment. 25 Both kidneys were denervated and both ureters catheterized. 24,25 The left kidney was placed in a stable cup, and a renal artery was side-branch catheterized.…”

Section: Surgical Proceduresmentioning

confidence: 99%

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Disparate Roles of AT ₂ Receptors in the Renal Cortical and Medullary Circulations of Anesthetized Rabbits

et al. 2003

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Abstract-The contributions of angiotensin II type 1 (AT 1 ) and type 2 (AT 2 ) receptors to the control of regional kidney blood flow were determined in pentobarbital-anesthetized rabbits. Intravenous candesartan (AT 1 antagonist; 10 g/kg plus 10 g · kg Ϫ1 · h Ϫ1) reduced mean arterial pressure (12%) and increased total renal blood flow (29%) and cortical laser-Doppler flux (18%) but not medullary laser-Doppler flux. Neither intravenous PD123319 (AT 2 antagonist; 1 mg/kg plus 1 mg · kg Ϫ1 · h Ϫ1 ) nor saline vehicle significantly affected these variables, and the responses to candesartan plus PD123319 were indistinguishable from those of candesartan alone. In vehicle-treated rabbits, renal-arterial infusions of angiotensin II (1 to 25 ng · kg Ϫ1 · min Ϫ1 ) and angiotensin III (5 to 125 ng · kg Ϫ1 · min Ϫ1) dose-dependently reduced renal blood flow (up to 51%) and cortical laser-Doppler flux (up to 50%) but did not significantly affect medullary laser-Doppler flux or arterial pressure. Angiotensin(1-7) (20 to 500 ng · kg Ϫ1 · min Ϫ1) had similar effects but of lesser magnitude. CGP42112A (20 to 500 ng · kg Ϫ1 · min Ϫ1) did not significantly affect these variables. After PD123319 administration, angiotensin II and angiotensin III dose-dependently increased medullary laser-Doppler flux (up to 84%), and reductions in renal blood flow in response to angiotensin II were enhanced. Candesartan abolished renal hemodynamic responses to the angiotensin peptides, even when given in combination with PD123319. We conclude that AT 2 receptor activation counteracts AT 1 -mediated vasoconstriction in the renal cortex but also counteracts AT 1 -mediated vasodilatation in vascular elements controlling medullary perfusion. These mechanisms might have an important effect on the control of medullary perfusion under conditions of activation of the renin-angiotensin system. Key Words: receptors, angiotensin Ⅲ kidney Ⅲ laser-Doppler flowmetry Ⅲ rabbits Ⅲ renal circulation T he medullary circulation contributes to the control of mean arterial pressure (MAP) and body fluid homeostasis. 1 However, the roles of angiotensin II type 1 (AT 1 ) and type 2 (AT 2 ) receptors in regulating regional kidney perfusion remain unclear. In rats and rabbits, infusions of angiotensin II reduce total renal blood flow (RBF) and cortical blood flow but have a lesser effect on medullary blood flow (MBF). [2][3][4][5] Angiotensin II can even increase MBF, especially when administered as a bolus. 6 -8 Nitric oxide synthase and/or cyclooxygenase blockade can enhance angiotensin II-induced reductions in MBF and abolish angiotensin II-induced increases in MBF, both of which are chiefly AT 1 mediated. 4,6 -12 However, the contributions of AT 2 receptors to these effects have received little attention, even though they are expressed in vessels that might contribute to MBF control (eg, afferent arterioles and vasa recta). 13 AT 2 -mediated counterregulatory vasodilatation can oppose AT 1 -mediated vasoconstriction. For example, in rat renalwrap hypertension, AT 2 re...

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Leptin signaling pathways in the central nervous system: interactions between neuropeptide Y and melanocortins

Rahmouni¹,

Haynes²

2001

BioEssays

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No other hormone has drawn more attention than leptin in recent studies on the control of appetite, body weight and obesity. This hormone is produced by adipose tissue and enters the brain via a saturable specific transport mechanism. Leptin acts in the hypothalamus to modulate food intake and heat production as well as several other neuroendocrine pathways. The mechanisms through which leptin exerts its central nervous effects are now better understood. Proopiomelanocortin- and neuropeptide Y-containing neurons in the hypothalamus have emerged as potent candidate mediators of leptin action. These two neuropeptides have been shown to exert opposing effects using different pathways. Recently, Cowley et al. (2001) described a new circuit in the regulation of neuronal activity by leptin with an interaction between these two pathways. These data add complexity to the mechanisms by which leptin achieves its effects in the central nervous system, but they also offer potential mechanisms to explain the phenomenon of leptin resistance observed in obesity.

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Effects of activation of vasopressin-V1-receptors on regional kidney blood flow and glomerular arteriole diameters

Cited by 22 publications

References 6 publications

Urine concentrating mechanism: impact of vascular and tubular architecture and a proposed descending limb urea-Na⁺cotransporter

Urine concentrating mechanism: impact of vascular and tubular architecture and a proposed descending limb urea-Na⁺cotransporter

Disparate Roles of AT ₂ Receptors in the Renal Cortical and Medullary Circulations of Anesthetized Rabbits

Leptin signaling pathways in the central nervous system: interactions between neuropeptide Y and melanocortins

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Effects of activation of vasopressin-V1-receptors on regional kidney blood flow and glomerular arteriole diameters

Cited by 22 publications

References 6 publications

Urine concentrating mechanism: impact of vascular and tubular architecture and a proposed descending limb urea-Na+cotransporter

Urine concentrating mechanism: impact of vascular and tubular architecture and a proposed descending limb urea-Na+cotransporter

Disparate Roles of AT 2 Receptors in the Renal Cortical and Medullary Circulations of Anesthetized Rabbits

Leptin signaling pathways in the central nervous system: interactions between neuropeptide Y and melanocortins

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Urine concentrating mechanism: impact of vascular and tubular architecture and a proposed descending limb urea-Na⁺cotransporter

Urine concentrating mechanism: impact of vascular and tubular architecture and a proposed descending limb urea-Na⁺cotransporter

Disparate Roles of AT ₂ Receptors in the Renal Cortical and Medullary Circulations of Anesthetized Rabbits