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Experimental selective elevation of renal medullary blood flow in hypertensive rats: evidence against short‐term hypotensive effect
Author(s) -
Bądzyńska B.,
Sadowski J.
Publication year - 2012
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/j.1748-1716.2012.02435.x
Subject(s) - bradykinin , renal medulla , endocrinology , medicine , renal blood flow , perfusion , medullary cavity , blood pressure , kidney , angiotensin ii , renal circulation , excretion , chemistry , receptor
Aim Renal medullary blood flow ( MBF ) can be selectively increased by intrarenal or systemic infusion of bradykinin ( B k) in anaesthetized normotensive rats. We reproduced this effect in a number of rat models of arterial hypertension and examined whether increased perfusion of the renal medulla can cause a short‐term decrease in blood pressure ( BP ) that is not mediated by increased renal excretion and depletion of body fluids. Methods In uninephrectomized S prague– D awley rats, BP was elevated to approx. 145 mmHg by acute i.v. infusion of noradrenaline ( NA ) or angiotensin II (Ang II ) (groups 1, 2), 2‐week exposure to high‐salt diet (3), high‐salt diet + chronic low‐dose infusion of A ng II using osmotic minipumps (4) or chronic high‐dose Ang II infusion on normal diet (5). Uninephrectomized spontaneous hypertensive rats ( SHR ) were also examined (6,7). To selectively increase medullary perfusion, in anaesthetized rats, bradykinin was infused during 30–75 min into the renal medullary interstitium or intravenously. Results and Conclusion Bradykinin increased outer‐ and inner‐medullary blood flow (laser‐ D oppler fluxes) by 10–20% in groups (1, 2), by 30–50% in groups (3, 4, 5) and approx. 20% in SHR (6, 7). The concurrent increase in total renal blood flow (Transonic probe) was < 3%. A minor (<3%) decrease in BP was seen only in rats acutely rendered hypertensive by NA or Ang II infusions; however, the decreases in BP and increases in medullary perfusion were not correlated. Thus, there was no evidence that in hypertensive rats, substantial selective increases in medullary perfusion can cause a short‐term decrease in BP .