Selective deep nephron hyperfiltration in uninephrectomized spontaneously hypertensive rats

Selective deep nephron hyperfiltration in uninephrectomized spontaneously hypertensive rats. Studies were carried out to determine the effect of uninephrectomy (UNX) on single nephron hemodynamics and proteinuria in the spontaneously hypertensive rat (SHR). Four groups were studied: two-kidney SHR and normotensive WKY controls; SHR + UNX and WKY + UNX. UNX was performed at age 8 to 10 weeks. Blood pressure and protein excretion were measured periodically, and micropuncture experiments of cortical nephrons were carried out at age 32 to 40 weeks. Systolic blood pressure was not significantly different between SHR and SHR + UNX. Protein excretion increased markedly in the SHR + UNX 6 months after UNX, as compared with the other three groups. In cortical nephrons, single nephron glomerular filtration rate (SNGFR) and plasma flow entering the glomeruli (SNPF) was lower in SHR + UNX than in WKY + UNX. Glomerular hydraulic pressure (P G ) during stopped flow was closely comparable in all groups, rising only 2mm Hg after UNX. SNGFR was measured in juxtamedullary (JM) nephrons 2 months after UNX, a stage before heavy proteinuria developed. We found that JM SNGFR was approximately 50% higher in SHR + UNX than in WKY + UNX. The observations suggest that following ablation of renal mass, superficial cortical glomeruli are not exposed to excessively high pressure or flow rates in the SHR. In contrast, JM glomeruli undergo a disproportionate rise in SNGFR, presumably associated with excessively high P G and/or blood flow. This medullary abnormality may predispose to selective damage of deep glomeruli, and proteinuria which emanates from JM nephrons. Hyperfiltration selective des nephrons profonds chez des rats spontanement hypertendus uninephrectomises. Des etudes ont ete effectuees afin de determiner l'effet de l'uninephrectomie (UNX) sur l'hemodynamique des nephrons individuels et sur la proteinurie chez des rats spontanement hypertendus (SHR). Quatre groupes ont ete etudies: des SHR et des controles normotendus WKY a 2 reins: des SHR + UNX, et des WKY + UNX. L'UNX etait effectuee a l'âge de 8 a 10 semaines. La pression arterielle et l'excretion des proteines etaient mesurees periodiquement, et des experiences de microponction des nephrons corticaux etaient effectuees a l'âge de 32 a 40 semaines. La pression arterielle systolique ne differait pas significativement entre SHR et SHR + UNX. L'excretion de proteines augmentait de facon marquee chez SHR + UNX 6 mois apres UNX, par rapport aus trois autres groupes. Dans les nephrons corticaux, le debit de filtration glomerulaire (SNGFR) et le flux plasmatique entrant dans les glomerules (SNPF) des nephrons individuels etaient plus bas dans SHR + UNX que dans WKY + UNX. La pression hydraulique glomerulaire (P G ) pendant l'interruption du flux etait tres voisine dans tous les groupes, ne s'elevant que de 2mm Hg apres UNX. SNGFR a ete mesuree dans les nephrons juxta-medullaires (JM) 2 mois apres UNX, au stade precedant le developpement d'une proteinurie abondante. Nous avons trouve que JM SNGFR etait environ 50% plus eleve chez SHR + UNX que chez WKY + UNX. Ces observations suggerent qu'apres ablation de la masse renale, les glomerules corticaux superficiels ne sont pas exposes a des pressions ou des debits excessivement hauts chez les SHR. A l'oppose, les glomerules JM subissent une augmentation disproportionnee de SNGFR, sans doute associee avec une P G et/ou un debit sanguin excessivement hauts. Cette anomalie medullaire pourrait predisposer a une alteration selective des glomerules profonds, et a la proteinurie qui provient des nephrons JM.