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  • 1
    Electronic Resource
    Electronic Resource
    RENAL VENOUS WEDGE PRESSURE IN RENAL WRAP HYPERTENSION IN RABBITS (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Clinical and experimental pharmacology and physiology 16 (1989), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Renal cellophane wrapping to produce hypertension causes thickening of the capsule of the kidney. To determine whether this compresses the kidney, deep renal vein wedge pressure was measured as an estimate of tissue pressure in anaesthetized rabbits 1 month after cellophane wrapping (n= 5) or a sham operation (n= 3).2. Renal vein wedge pressure was 18.3 ± 2.0 mmHg in hypertensive rabbits and 8.4 ± 1.1 mmHg in the sham-operated rabbits.3. Arterial pressure was raised or lowered with angiotensin II or glyceryl trinitrate, respectively. Arterial and wedge pressures were approximately linearly related and, at any given arterial pressure, wedge pressure was approximately 8 mmHg higher in the cellophane-wrapped kidney than in the kidney of the sham-operated group.4. These results, showing that renal wedge pressure is elevated in renal wrap rabbits, indicate that the kidneys are compressed, probably by the thickened renal capsule. This may explain the increased renal vascular resistance seen in this form of hypertension.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.1989.tb01621.x
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  • 2
    Electronic Resource
    Electronic Resource
    NEURAL CONTROL OF RENAL MEDULLARY PERFUSION (2004)
    Oxford, UK : Blackwell Science Pty
    Clinical and experimental pharmacology and physiology 31 (2004), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. There is strong evidence that the renal medullary circulation plays a key role in long-term blood pressure control. This, and evidence implicating sympathetic overactivity in development of hypertension, provides the need for understanding how sympathetic nerves affect medullary blood flow (MBF).2. The precise vascular elements that regulate MBF under physiological conditions are unknown, but likely include the outer medullary portions of descending vasa recta and afferent and efferent arterioles of juxtamedullary glomeruli, all of which receive dense sympathetic innervation.3. Many early studies of the impact of sympathetic drive on MBF were flawed, both because of the methods used for measuring MBF and because single and often intense neural stimuli were tested.4. Recent studies have established that MBF is less sensitive than cortical blood flow (CBF) to electrical renal nerve stimulation, particularly at low stimulus intensities. Indeed, MBF appears to be refractory to increases in endogenous renal sympathetic nerve activity within the physiological range in all but the most extreme cases.5. Multiple mechanisms appear to operate in concert to blunt the impact of sympathetic drive on MBF, including counter-regulatory roles of nitric oxide and perhaps even paradoxical angiotensin II-induced vasodilatation. Regional differences in the geometry of glomerular arterioles are also likely to predispose MBF to be less sensitive than CBF to any given vasoconstrictor stimulus.6. Failure of these mechanisms would promote reductions in MBF in response to physiological activation of the renal nerves, which could, in turn, lead to salt and water retention and hypertension.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.2004.04003.x
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  • 3
    Electronic Resource
    Electronic Resource
    Metalloendopeptidases EC 3.4.24.15 and EC 3.4.24.16 And Bradykinin B2 Receptors Do Not Play Important Roles In Renal Wrap Hypertension In Rabbits (2001)
    Melbourne, Australia : Blackwell Science Pty
    Clinical and experimental pharmacology and physiology 28 (2001), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The aim of the present study was to determine the effects of the metalloendopeptidase (EP) 24.15 and 24.16 inhibitor N-[1-(R,S)-carboxy-3-phenylpropyl]-Ala-Aib-Tyr-p-aminobenzoate (JA-2) on haemodynamics and renal function in conscious rabbits with two-kidney, two-wrapped hypertension. We have also examined the role of endogenous bradykinin in the maintenance phase of this form of renovascular hypertension and whether inhibition of bradykinin degradation contributes to any potential effects of JA-2.2. In two preliminary operations, rabbits were equipped with transit-time ultrasound flow probes for measuring cardiac output (CO) and renal blood flow (RBF) and had both kidneys wrapped in cellophane. Starting 4 weeks after the last operation, rabbits underwent four studies (3–5 days apart), during which they were treated with combinations of the bradykinin B2 receptor antagonist icatibant or its vehicle (1 mL/kg bodyweight 0.9% w/v NaCl) and JA-2 or its vehicle (1 mL/kg of a 5% w/v 2-hydroxypropyl-β-cyclodextrin, 2.5% v/v dimethylsulphoxide solution). Renal function was monitored using standard renal clearance methods.3. Icatibant (10 μg/kg) had no significant effects on systemic haemodynamic variables (mean arterial pressure, heart rate or CO), renal haemodynamic variables (RBF or glomerular filtration rate), urine flow or sodium excretion. At 5 mg/kg plus 3 mg/kg per h, JA-2 also did not affect any of these variables, either after icatibant vehicle treatment or after icatibant treatment.4. Our data do not support major roles for endogenous bradykinin or bradykinin degradation by EP 24.15/24.16 in the control of systemic and renal haemodynamics or renal excretory function in two-kidney, two-wrapped hypertension in rabbits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1440-1681.2001.03532.x
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  • 4
    Electronic Resource
    Electronic Resource
    EFFECT OF ENDOTHELIN-1 ON REGIONAL KIDNEY BLOOD FLOW AND RENAL ARTERIOLE CALIBRE IN RABBITS (2004)
    Oxford, UK : Blackwell Science Pty
    Clinical and experimental pharmacology and physiology 31 (2004), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Medullary blood flow (MBF) is important in the long-term control of arterial pressure. However, it is unclear which vascular elements regulate MBF.2. Exogenous endothelin (ET)-1 decreases cortical more than medullary blood flow. We hypothesized that ET-1 would therefore constrict afferent (AA) and efferent arterioles (EA) of juxtamedullary glomeruli less than those of cortical glomeruli.3. Mean arterial pressure, renal blood flow and cortical (CBF) and medullary (MBF) blood flow, via laser-Doppler flowmetry, were measured before and after intrarenal ET-1 (2 ng/kg per min; n = 6) or vehicle (n = 6) in anaesthetized rabbits. Kidneys were perfusion fixed, vascular casts formed, lumen diameters measured via scanning electron microscopy and relative resistance calculated.4. Mean arterial pressure was not significantly affected by ET-1 infusion. Cortical glomerular arteriole lumen diameters were significantly reduced in the ET-1-infused group (AA approximately 30%, EA approximately 18%; PA 〈 0.01), compatible with the decrease in CBF (42 ± 3%; PGT 〈 0.01). Juxtamedullary arteriole lumen diameters were also significantly reduced in the ET-1-infused group (AA approximately 34%, EA approximately 21%; PA 〈 0.01); however, MBF did not decrease.5. In conclusion, our data suggest that juxtamedullary arterioles are not of primary importance in the regulation of MBF because, despite reductions in juxtamedullary arteriole diameters in response to ET-1, MBF was not decreased.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.2004.04036.x
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  • 5
    Electronic Resource
    Electronic Resource
    DIFFERENTIAL NEURAL CONTROL OF GLOMERULAR ULTRAFILTRATION (2004)
    Oxford, UK : Blackwell Science Pty
    Clinical and experimental pharmacology and physiology 31 (2004), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. The renal nerves constrict the renal vasculature, causing decreases in renal blood flow (RBF) and glomerular filtration rate (GFR). Whether renal haemodynamics are influenced by changes in renal nerve activity within the physiological range is a matter of debate.2. We have identified two morphologically distinct populations of nerves within the kidney, which are differentially distributed to the renal afferent and efferent arterioles. Type I nerves almost exclusively innervate the afferent arteriole whereas type II nerves are distributed equally on the afferent and efferent arterioles. We have also demonstrated that type II nerves are immunoreactive for neuropeptide Y, whereas type I nerves are not.3. This led us to hypothesize that, in the kidney, distinct populations of nerves innervate specific effector tissues and that these nerves may be selectively activated, setting the basis for the differential neural control of GFR. In physiological studies, we demonstrated that differential changes in glomerular capillary pressure occurred in response to graded reflex activation of the renal nerves, compatible with our hypothesis.4. Thus, sympathetic outflow may be capable of selectively increasing or decreasing glomerular capillary pressure and, hence, GFR by differentially activating separate populations of renal nerves. This has important implications for our understanding of the neural control of body fluid balance in health and disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.2004.04002.x
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