title: Threshold pressure for the pressure-dependent renin release in the autoregulating kidney of conscious dogs.
abstract: The effect of varying renal artery pressure between 160 and 40 mm Hg on renal blood flow and renin release was studied in seven conscious foxhounds under beta-adrenergic blockade receiving a normal sodium diet (4.1 mmol/kg/day). Pressure was either increased by bilateral common carotid occlusion or reduced in steps and maintained constant by a control-system using an inflatable renal artery cuff. Carotid occlusion itself had no influence on renal blood flow and renin release when renal artery pressure was kept constant and the beta-receptors in the kidney were blocked. Between 160 mm Hg and resting pressure there was no change in renal blood flow; between resting blood pressure and the lower limit of autoregulation (average 63.9 mm Hg) renal blood flow increased slightly (average 7%) indicating a high efficiency of renal blood flow autoregulation. The relationship between renal artery pressure and renin release could be approximated by two linear sections: a low sensitivity to a pressure change (average slope: -0.69 +/- 0.26 ng AI/min/mm Hg) was found above a threshold pressure (average: 89.8 +/- 3.3 mm Hg) and a high sensitivity to a pressure change (average slope: -64.4 +/- 20.8 ng AI/min/mm Hg) was observed between threshold pressure and 60 mm Hg. There was no further increase of renin release between 60 and 40 mm Hg.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure; D002339:Carotid Arteries / Q000502:physiology; D004285:Dogs; D006706:Homeostasis; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D010477:Perfusion; D011311:Pressoreceptors / Q000502:physiology*; D012077:Renal Artery / Q000502:physiology*; D012079:Renal Circulation / Q000187:drug effects; D012083:Renin / Q000378:metabolism*
chemical_list: D000319:Adrenergic beta-Antagonists; D012083:Renin