Laboratory Investigation

Kidney International (1985) 27, 731–738; doi:10.1038/ki.1985.73

Pressure dependence of exaggerated natriuresis in two-kidney, one clip Goldblatt hypertensive rats

H S Mackenzie1, A L Morrill1 and David W Ploth1

1Birmingham Veterans Administration Medical Center, and Nephrology Research and Training Center, Department of Medicine, University of Alabama in Birmingham Medical Center, University Station, Birmingham, Alabama, USA

Correspondence: Dr D W Ploth, Division of Nephrology, University of Alabama in Birmingham, University Station - 727 CDLD, Birmingham, Alabama 35294, USA

Received 2 May 1984; Revised 9 October 1984.

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Abstract

Pressure dependence of exaggerated natriuresis in two-kidney, one clip Goldblatt hypertensive rats. This study evaluated the responses of each kidney of two-kidney, one clip Goldblatt hypertensive rats to acute volume loading to delineate the contribution of elevated perfusion pressure to the mechanisms of the exaggerated natriuresis in this model of hypertension. Eleven Goldblatt animals (0.2 mm clip 3 weeks prior to study) were studied at spontaneous blood pressure for each kidney's response to volume loading. In 11 other Goldblatt animals an aortic clamp between the renal arteries allowed reduction of perfusion pressure for the left, nonclipped kidney to normal levels. Ten normal rats served as controls. Renal function was examined during control periods and following the infusion of 3.5% body wt of 154 mM dot liter-1 NaCl at 22.5 mldothr-1. An exaggerated natriuresis was observed for the left, nonclipped kidney of the hypertensive Goldblatt rats, while the clipped kidney exhibited an attenuated natriuresis compared to either kidney of normal control rats. Reduction of perfusion pressure to the nonclipped kidney of Goldblatt animals to normal levels resulted in reduced clearance and excretory function before volume loading and attenuated its natriuretic response to levels less than those for the Goldblatt group at spontaneous, hypertensive blood pressure. The exaggerated natriuresis observed at hypertensive blood pressure was attributable to increases of filtered load of Na+ and reduced fractional absorption. These observations indicate that an exaggerated natriuresis occurs in the two-kidney, one clip Goldblatt hypertensive rat and that this phenomenon depends on the elevated renal perfusion pressure to the nonclipped kidney.

Natriurèse exagérée, dépendant de la pression, chez des rats Goldblatt hypertendus deux reins, un clip. Cette étude a évalué les réponses de chaque rein de rats Goldblatt hypertendus à deux reins, un clip, à une surcharge volémique aiguë pour préciser la contribution de l'élévation de pression de perfusion aux mécanismes de la natriurèse exagérée dans ce modèle d'hypertension. Onze animaux Goldblatt (clip de 0,2 mm 3 semaines avant l'étude) ont été étudies à leur pression sanguine spontanée pour chaque réponse rénale à une expansion volémique. Chez 11 autres animaux Goldblatt un clamp aortique entre les artères rénales permettait une réduction de la pression de perfusion du rein gauche, non clippé à des valeurs normales. Dix rats normaux servaient de contrôles. La fonction rénale a été étudiée pendant des périodes contrôles et après perfusion de 3,5% du poids corporel de 154 mM dot litre-1 NaCl à 22,5 ml dot hr-1. Une natriurèse exagérée a été observée pour le rein gauche, non-clippé des Goldblatt hypertendus, alors que le rein clippé présentait une natriurèse atténuée par rapport à chacun des reins des rats contrôles normaux. Une réduction de la pression de perfusion dans le rein non clippé des animaux Goldblatt à des valeurs normales entrainait une réduction de clearance et de fonction excrétrice avant l'expansion volémique, et atténuait sa réponse natriurétique à des niveaux moindres que ceux du groupe Goldblatt à une pression sanguine spontanée, hypertendue. La natriurèse exagérée observée pour des pressions sanguines hypertendues était attribuable à des élévations de la charge filtrée de Na+ et à une réabsorption fractionnelle réduite. Ces observations indiquent qu'une natriurèse exagérée se produit chez le rat hypertendu Goldblatt à deux reins, un clip, et que ce phénomène dépend d'une pression de perfusion rénale élevée dans le rein non clippé.

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