Invited Symposium: Hypertension II: Hypertension and Vascular Control



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Renal Microvascular Reactivity to Angiotensin II is Enhanced in Angiotensin II-Induced Hypertension

Imig, J.D. (Department of Physiology, Tulane University School of Medicine, USA)

Contact Person: John D. Imig (jdimig@mailhost.tcs.tulane.edu)


The current studies were performed to determine renal microvascular tone and reactivity in angiotensin II-infused hypertensive rats. Male-Sprague Dawley rats received angiotensin II (60 ng/min) or vehicle via an osmotic minipump. Angiotensin II-infused hypertensive and normotensive shams were studied 5-7 and 11-13 days following implantation of the minipump. Systolic blood pressure (SBP) averaged 117 plusmn; 4 mmHg (n=31) prior to pump implantation. Angiotensin II infusion increased SBP to 155 plusmn; 7 (n=6) and 184 plusmn; 6 mmHg (n=9) on infusion day 6 and 12, respectively. Renal microvascular responses to angiotensin II, norepinephrine or increasing perfusion pressure were observed utilizing the in vitro juxtamedullary nephron preparation. At a renal perfusion pressure of 80 mmHg interlobular and afferent arteriolar diameters of normotensive animals averaged 28 plusmn; 1 micrometer and 18 plusmn; 1 micrometer, respectively. Diameters of the interlobular arteriole at renal artery perfusion pressures between 80 and 160 mmHg were 12-20% smaller in 11-13 day hypertensive rats compared to normotensive controls. Additionally, 5-7 and 11-13 day hypertensive animals had an enhanced responsiveness of the renal microvasculature to angiotensin II. Angiotensin II (10 nM) decreased afferent arteriolar diameter by 27 plusmn; 3% in the 5-7 day hypertensive group, by 19 plusmn; 3% in 11-13 day hypertensive group and by 13 plusmn; 3% in normotensive animals. In contrast, the afferent arteriolar response to norepinephrine was not enhanced after 5-7 days on angiotensin II administration. These data demonstrate an enhanced renal microvascular tone and enhanced vascular reactivity which is selective for angiotensin II in animals which develop hypertension following infusion of angiotensin II.

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Presentation Number SAimig0781
Keywords: kidney, hypertension, microcirculation, hemodynamics

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Imig, J.D.; (1998). Renal Microvascular Reactivity to Angiotensin II is Enhanced in Angiotensin II-Induced Hypertension. Presented at INABIS '98 - 5th Internet World Congress on Biomedical Sciences at McMaster University, Canada, Dec 7-16th. Invited Symposium. Available at URL http://www.mcmaster.ca/inabis98/boegehold/imig0781/index.html
© 1998 Author(s) Hold Copyright