Renal blood flow measured with xenon-133 wash-out technique and with an electromagnetic flowmeter

Summary 30 simultaneous measurements of the renal cortical blood flow with the xenon-133 wash-out technique and the total renal blood flow with an electromagnetic flowmeter were performed in eight dogs. Renal blood flow was varied over a wide range. A highly significant correlation was found between the two measurements. The slope of the correlation line was 1.18 and the standard error of the estimate was 0.81 ml/g cortex × min.With 2 Figures in the TextWith the aid of the Deutsche Forschungsgemeinschaft.National Science Foundation Fellow to Göttingen. Permanent address: Department of Physiology, Indiana University, School of Medicine, Indianapolis.     

Renal blood flow during ureteral obstruction measured with133Xe wash out,86Rb uptake techniques and with an electromagnetic flowmeter

Summary In moderate mannitol diuresis in the dog the ratio RBF-⁸⁶Rb uptake/RBF-electromagnetic flowmeter decreased during ureteral obstruction from 0.923–0.705. In the same animals the ratio RBF-¹³³Xe wash-out/RBF-electromagnetic flowmeter increased from 0.932–1.365. With the rubidium technique a significant redistribution of intrarenal blood flow was observed. No similar flow changes were seen with the¹³³Xe wash-out technique. The two methods do not measure during ureteral obstruction the true RBF. The change of⁸⁶Rb uptake by the individual segments of renal tissue is not an unequivocal proof for the intrarenal redistribution of bloof flow, but this possibility cannot be definitely excluded.     

Radioactive microsphere distribution and single glomerular blood flow in the normal rabbit kidney

Summary Intracortical distribution of blood flow was studied in the rabbit kidney with 15 m labelled microspheres (M) injected into the left ventricule. M injection did not alter renal function. Thanks to arterial filling of left kidney with silicone rubber, efferent vascular patterns of the glomeruli could be precisely identified. Glomeruli of different populations were sampled by microdissection and their radioactivity measured. Assuming that intracortical distribution of M reflected distribution of flow to the glomeruli, individual glomerular blood flows (GBF) were determined. In hydropenic rabbits, GBF was higher in deep glomeruli providing vasa recta (G4) (193±14 nl·min^–1) than in most other superficial (G1 and G2) and deep glomeruli (G3) (190±27, 113±10 and 127±9 nl·min^–1 respectively; . The exact significance of GBF found in superficial glomeruli with straight ascending efferent arterioles supplying aglomerular suscapsular cortex (G1) was questioned because of the possible axial streaming of spheres. Afferent medulary blood flow was calculated to represent 9.0±0.9% of total renal blood flow.Attaché de Recherches I.N.S.E.R.M.     

High-frequency microcinematographic measurements on peritubular blood flow under control conditions and after temporary ischemia of rat kidneys

Summary The incident-light, high-frequency microcinematography of the kidney surface of rats is described as a new method for investigating renal microcirculation. The welling point area served as the anatomical reference point for microcirculatory measurements. In the first section of vessel distal to the welling point the average flow velocity was 2.32±0.24 mm/sec; the diameter was 15.91±0.92 microns. Flow rate in the efferent arteriole, calculated from the flow rate in the first vessel section distal to the welling point and the degree of ramification, was 103 nl/min. The results closely agree with total renal blood flow that was determined simultaneously.As an example for measurements taken under different conditions, a model for experimental acute renal failure was chosen. In kidneys subjected to a 60 min period of ischemia three days prior to use, the peritubular blood flow at the kidney surface was decreased only by 1/4; the difference in the means was insignificant. Therefore, a lasting cortical ischemia cannot be the only cause for the persistent oliguria in experimental acute renal failure.Supported by the Deutsche Forschungsgemeinschaft (SFB 90).Presented in part at the VII Symposion der Gesellschaft für Nephrologie, Tübingen, 1970, and the XXV International Congress of Physiological Sciences, München, 1971.     

Excretion and tubular reabsorption of sodium,glucose and phosphate by isolated dog kidneys. Influence of blood dilution

Summary Sodium, glucose and phosphate reabsorption and excretion have been investigated in totally isolated dog kidneys. The potentiation by furosemide of the natriuresis caused by saline loading of the preparation is quantitatively comparable to that observed in the whole animal; the decrease of proximal reabsorption together with its partial distal compensation correspond primarily to a direct renal effect of blood dilution. Glucose reabsorption is proportional to glomerular filtration rate; it does not differ from the values found in the whole dog. Phosphate reabsorption is proportional to the filtered phosphate load up to a value of the latter of 10 mg P/min/100 g; at higher values a true TmPO₄ is reached which is higher than in normal or thyroparathyroidectomized dogs. Blood dilution exhibits no influence on TmG. The influence of blood dilution on fractional P reabsorption depends on the P filtered load. At low values of this load, P reabsorption is not influenced; at high values, reabsorption is significantly reduced by dilution. No relationship is demonstrated between glucose and sodium reabsorption inasmuch as the latter is under direct dependence on blood dilution. Furosemide (10^–4 M) induces no significant change in either TmG, P reabsorption or glomerular filtration rate.     

Renal cortical blood flow distribution measured by hydrogen clearance during dopamine and acetylcholine infusion. Effect of electrode thickness and position in cortex

Blood flow distribution in the renal cortex was investigated in control and during i.a. infusion of dopamine (DA) and acetylcholine (Ach) in dogs. Local blood flow in outer cortex (OCF) and in inner cortex (ICF) was measured by platinum electrodes detecting hydrogen washout rate in tissue. Mean cortical blood flow measured by hydrogen washout rate in the renal vein (CFV) was compared with renal arterial blood flow (RAF) measured by electromagnetic flowmeter. With electrodes of 0.05–0.2 mm diameter control blood flow rates in outer and inner cortex were 4.57± (S.D.) 1.73 ml/min g and 4.35±0.57 ml/min g, which is higher than found using 0.2–0.5 mm electrodes in this and previous studies. OCF and ICF increased proportionally during intraarterial infusion of DA or Ach. The increase in local blood flow per unit volume was about 20% less than the increase in RAF, most likely due to an increase in renal volume and a reduced vasodilatory response in the surrounding of some electrodes. CFV rose almost to the same degree as RAF, showing a diffusion equilibrium for hydrogen gas even at maximal flow rate. During vasoconstriction induced by high doses of DA, OCF and ICF fell proportionately. Thus, equal vascular responses in outer and inner cortex were observed during both vasodilator and vasoconstrictor infusion. This indicates that changes in sodium excretion with renal blood flow may not be associated with a redistribution of cortical peritubular blood flow.