A modified
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Xe washout technique was used to study changes in intrarenal hemodynamics during glycerol-induced acute renal failure in the rat. Within 10 minutes after glycerol injection, the flow fraction supplied to component 1 of the washout curve ("cortex A") decreases, reaching minimum values 24 hours afer glycerol (31% of control conditions). Seven days thereafter five of the rats, still uremic, showed cortical flow fractions less than 50% of control values. Nine others had recovered. Twenty-four hours after glycerol, renal blood flow was 27% and increased to 86% of control conditions in the recovered rats 7 days after glycerol.
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Kr autoradiographs and silicone rubber casts of the renal vasculature demonstrated a severe cortical hypoperfusion at the height of oliguria that gradually disappeared in parallel with the functional recovery of the kidney. These observations, in good agreement with micropuncture data, suggest that oliguria and renal insufficiency in this experimental model are the result of a primary decrease in glomerular filtration rate due to an increased preglomerular resistance.
Intrarenal distributionof urea and related compounds: effects of nitrogen intake.Am. J. Physiol. 207(s) : 971-978. rg64.-Nitrogen and NaCl intake influence the excretion of urea. In rats maintained on a low-protein, high-salt intake the urea-to-inulin clearance ratio decreases to 0.01. In antidiuretic "low-protein" rats the urea concentrations in the inner medulla are higher than in the urine, whereas in rats on high-protein diet the urea concentration in the inner medulla is lower than in the urine. The specific activity of urea-Cl4 I hr after subcutaneous injection is approximately the same in plasma, renal cortex, and outer and inner medulla. The intrarenal distributions of acetamide and methylurea show the same pattern and are influenced by nitrogen intake in the same way as urea, whereas thiourea concentrations in urine are always higher than in the papilla. It is concluded a) that urea formation cannot account for papilla urea concentrations higher than urine concentrations; b) that the handling of urea and related compounds in the collecting duct changes in a similar way with changes in the nitrogen and salt intake; and c) that in the rat urea, methylurea, and acetamide are either reabsorbed in the collecting duct against their concentration gradients or bound by the papilla tissue. methylurea acetamide urea reabsorption thiourea urea excretion
Summary. Serial measurements of intrarenal distribution of blood flow have been recorded in anesthetized dogs with the 133xenon "washout" technique. The results showed that normal kidneys redistributed their blood flow after laparotomy and mobilization of the kidney. This alteration consisted of a diminution in percentage of total renal blood flow supplied to the fastest flowing component, and a diminution of renal mass supplied by that component. This effect lasted for as long as 7 days. Thereafter, the blood flow distribution remained stable.Autotransplanted kidneys had a stable distribution of blood flow between 0 and 77 days after operation, the values being identical with the stable normal kidney. Homotransplanted kidneys had the same intrarenal distribution of blood flow after operation as the autotransplanted kidneys. Whereas the intrarenal distribution of blood flow of the autotransplanted kidneys remained stable, a redistribution occurred in the homotransplanted kidneys as rejection progressed.. This phenomenon occurred before marked elevation of blood urea nitrogen.The redistribution was due to a decrease in percentage of blood flow supplied to the fastest flowing component, and a relative reduction of tissue mass perfused by this component.Radioautography of the kidneys before rejection demonstrated that the cortex was homogeneously perfused by the fastest flowing component of blood flow. As rejection progressed, a reduced area of cortex was perfused by this component. Terminally, the fastest flowing component was located in the outer medulla.It is suggested that the reduction in cortical blood flow produced by immunological mechanisms may play a prominent role in the ensuing renal failure.
IntroductionAnatomical changes in the intrarenal vasculature are a prominent feature in the homotransplated *
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