Laboratory Investigation

Kidney International (1983) 23, 816–822; doi:10.1038/ki.1983.100

Effects of unclipping and converting enzyme inhibition on bilateral renal function in Goldblatt hypertensive rats

Wann-Chu Huang1 and L Gabriel Navar1

1Department of Physiology and Biophysics, Nephrology Research and Training Center, University of Alabama in Birmingham Medical Center, Birmingham, Alabama

Correspondence: Dr L G Navar, Department of Physiology and Biophysics, Nephrology Research and Training Center, University of Alabama in Birmingham Medical Center, University Station, 727 CDLD Building, Birmingham, Alabama 35294, USA

Received 2 April 1982; Revised 24 August 1982.

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Abstract

Effects of unclipping and converting enzyme inhibition on bilateral renal function in Goldblatt hypertensive rats. Previous studies have demonstrated that blockade of the renin-angiotensin system in two-kidney, one clip Goldblatt hypertensive rats induced arterial pressure associated reductions in the function of the renin rich, clipped kidney even though the renin-depleted, contralateral kidney exhibited enhanced renal hemodynamics and excretory function. This study was performed to evaluate the influence of inhibition of the activity of the renin-angiotensin system on the function of each kidney following the unclipping of the clipped kidney. Renin-angiotensin system blockade was accomplished by intravenous infusion of converting enzyme inhibitor (CEI, SQ 20881, 3 mg/hr dot kg), either before (group 1, N = 15) or after (group 2, N = 16) removal of the clip. CEI infusion before unclipping decreased arterial blood pressure (BP), from 157 plusminus 3 to 124 plusminus 3 mm Hg and led to increases in renal blood flow (RBF), GFR, urinary volume and sodium excretion in the nonclipped kidney. When the clip was still in place, renal function decreased in the clipped kidney during CEI infusion. Upon removal of the clip, there were immediate increases in RBF and GFR, and pronounced diuresis; natriuresis and kaliuresis ensued despite a further reduction of BP from 124 plusminus 3 to 110 plusminus 3 mm Hg. In group 2, unclipping of the clipped kidney prior to administration of CEI reduced BP from 161 plusminus 4 to 118 plusminus 3 mm Hg within 2 hr. Nevertheless, RBF, GFR, urine flow, and sodium and potassium excretion rates increased in this newly undipped kidney. Subsequent infusion of CEI decreased BP further, but RBF, GFR, and urinary excretion rates of both kidneys increased significantly. These results suggest that hemodynamic and excretory function of both the nonclipped and clipped kidneys are influenced substantially by the renin-angiotensin system; however, this influence on the clipped kidney can be unmasked only after the clip has been removed.

Effets de l'ablation du clip et de l'inhibition de l'enzyme de conversion sur la fonction rénale bilatérale chez des rats hypertendus selon Goldblatt. Les études antérieures ont démontré que le blocage du système rénine-angiotensine chez des rats hypertendus selon Goldblatt à deux reins et un clip entrainait des réductions de la fonction du rein riche en rénine clippé, en rapport avec la pression artérielle, bien que le rein contralatéral, déplété en rénine, ait une augmentation de l'hémodynamique et de la fonction excrétoire rénales. Cette étude a été entreprise afin d'évaluer l'influence de l'inhibition de l'activité du système rénine-angiotensine sur la fonction de chaque rein après ablation du clip du rein clippé. Le blocage du système rénine-angiotensine a été effectué par perfusion intra-veineuse de l'inhibiteur de l'enzyme de conversion (CEI, SQ 20881, 3 mg/hr dot kg) soit avant (groupe 1, N = 15) soit après (groupe 2, N = 16) ablation du clip. La perfusion de CEI avant l'ablation du clip a abaissé la pression artérielle (BP) de 157 plusminus 3 à 124 plusminus 3 mm Hg, et a augmenté le flux sanguin (RBF), le GFR, le volume urinaires et l'excrétion sodée du rein non clippé. Lorsque le clip était encore en place, la fonction rénale diminuait du côté du rein clippé pendant la perfusion de CEI. Lors de l'ablation du clip, il y avait des augmentations immédiates du RBF et de GFR et une diurèse; une natriurèse et une kaliurèse prononcées se produisaient malgré une réduction supplémentaire de la BP de 124 plusminus 3 à 110 plusminus 3 mm Hg. Dans le groupe 2, l'ablation du clip avant l'administration de CEI a réduit la BP du rein clippé de 161 plusminus 4 à 118 plusminus 3 mm Hg en 2 hr. Cependant, le RBF, le GFR, le débit urinaire, et l'excrétion de sodium et de potassium se sont élevés dans ce rein dont le clip a été récemment enlevé. La perfusion ultérieure de CEI diminuait BP plus mais RBF, GFR, et les excrétions urinaires des deux reins ont augmenté significativement. Ces résultats suggèrent que les fonctions hémodynamique et excrétoire des reins clippés et non-clippés sont substantiellement influencées par le système rénine-angiotensine; cependant, cette influence sur le rein clippé ne peut être démasquée qu'après ablation du clip.

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