Laboratory Investigation

Kidney International (1985) 28, 128–134; doi:10.1038/ki.1985.131

Nephron responses to converting enzyme inhibition in non-clipped kidney of Goldblatt hypertensive rat at normotensive pressures

Wann-Chu Huang1, Cynthia A Jackson1 and L Gabriel Navar1

1Department of Physiology and Biophysics and Nephrology Research and Training Center, University of Alabama at Birmingham, Birmingham, Alabama, USA

Correspondence: Dr L G Navar, University of Alabama at Birmingham, University Station—727 CDLD, Birmingham, Alabama 35294 USA.

Received 20 June 1984; Revised 22 February 1985.

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Abstract

Nephron responses to converting enzyme inhibition in non-clipped kidney of Goldblatt hypertensive rat at normotensive pressures. To evaluate the effects of angiotensin converting enzyme inhibition (SQ 20881, CEI) on superficial nephron function of the non-clipped kidney in Goldblatt hypertensive rats in the absence of alterations in renal arterial pressure, control renal arterial pressure (RAP) was reduced first to the range generally obtained during CEI (124 plusminus 4 mm Hg). RAP was maintained during the CEI period by adjustment of a suprarenal aortic clamp. At the reduced RAP, whole kidney and single nephron glomerular filtration rates (GFR) were reduced from the hypertensive levels and were lower than the measurements in normotensive control rats. During CEI, whole kidney GFR and single nephron GFR increased by 55 and 42%, respectively. There were decreases in absolute as well as fractional proximal reabsorption rates. In the intermediate nephron segment, fractional reabsorption was decreased, but absolute fluid reabsorption increased in proportion to the increased delivery rate. Proximal tubule and peritubular capillary hydrostatic pressures increased significantly during CEI also. These results indicate that an increased activity of the renin-angiotensin system occurring in Goldblatt hypertensive rats subjected to aortic constriction exerts effects to lower GFR and increase proximal reabsorption rate. The concomitant superficial nephron and whole kidney GFR responses to CEI when arterial pressure was maintained suggests that the preexisting levels of angiotensin exerted similar influences on the total nephron population.

Réponses du néphron à l'inhibition de l'enzyme de conversion dans le rein non clippé de rats hypertendus Goldblatt pour des pressions normales. Afin d'évaluer les effets de l'inhibition de l'enzyme de conversion de l'angiotensine (SQ 20881, CEI) sur la fonction des néphrons superficiels du rein non clippé de rats hypertendus Goldblatt en l'absence d'altération de la pression artérielle rénale, la pression artérielle rénale contrôle (RAP) a d'abord été diminuée aux valeurs généralement obtenues pendant CEI (124 plusminus 4 mm Hg). RAP a été maintenue pendant la période de CEI par ajustement d'un clamp aortique sus-rénal. A une RAP réduite, les débits de filtration glomérulaire (GFR) rénal totale et néphronique individuelle étaient réduits par rapport au niveau hypertendu, et étaient plus faibles que les valeurs des rats normotendus contrôles. Au cours de CEI, GFR du rein entier et GFR néphronique individuelle ont augmenté de 55 et 42%, respectivement. Il existait des diminutions des débits de réabsorption absolus et fractionnels proximaux. Dans le segment néphronique intermédiaire, la réabsorption fractionnelle était diminuée, mais la réabsorption absolue de liquides augmentait en proportion de l'accroissement du débit délivré. Les pressions hydrostatiques tubulaires proximales et capillaires péritubulaires ont également augmenté significativement pendant CEI. Ces résultats indiquent qu'une augmentation de l'activité du système rénine angiotensine chez des rats hypertendus Goldblatt soumis à une constriction aortique a pour effet d'abaisser GFR et d'augmenter le débit de réabsorption proximale. Les réponses concomittantes de GFR du néphron superficiel et du rein entier à CEI lorsque la pression artérielle était maintenue suggèrent que les niveaux préexistants d'angiotensine ont exercé des influences identiques sur l'ensemble de la population néphronique.

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