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  • 1
    Electronic Resource
    Electronic Resource
    Tubuloglomerular feedback control in kidneys of adrenalectomized rats (1980)
    Springer
    Pflügers Archiv 386 (1980), S. 11-19 
    Details
    ISSN: 1432-2013
    Keywords: Adrenalectomy ; Tubuloglomerular feedback ; Intratubular stop flow pressure ; Loop of Henle ; Diluting capacity ; Renal renin content ; Dexamethasone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The technique of orthograde tubular microperfusion has been used to test the functional integrity of tubuloglomerular feedback control in adrenalectomized rats. Kidneys of these animals display high renin contents, as well as an impairment of electrolyte transport in the loop of Henle, which was demonstrated by monitoring the electrical conductivity of fluid entering the distal tubule over a perfusion range of 10–50 nl/min. The calculated electrolyte concentration of the perfusion fluid leaving the loop of Henle was significantly higher in adrenalectomized rats than in controls. Intratubular stop flow pressure (SFP) during perfusion with a modified “endproximal” Ringer's solution was recorded continuously in early proximal segments at rates of 0–40 nl/min. Direct pressure transmission from perfused endproximal tubular segments to the pressure recording capillary was prevented by paraffin blockade of the intermediate proximal segment. An intact feedback response in each of the 32 tubules of the adrenalectomized rats studied was observed, which was reversible and could be demonstrated repetitively in individual tubules. Thus ΔSFP at 40 nl/min was −11.2±1.3 mm Hg in adx rats as compared to −8.1±1.3 in control rats. An increased freedback sensitivity was observed in dexamethasone treated adrenalectomized rats despite normal renal renin content. Here ΔSFP at 40 nl/min was −15±1.1. Thus, the feedback signal can be mediated in the apparent absence of adrenal steroid hormones and a high sensitivity of tubuloglomerular feedback control is not necessarily paralleled by high renin content of renal tissue.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584181
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  • 2
    Electronic Resource
    Electronic Resource
    Das Verhalten der Plasmareninkonzentration nach akuter Natriurese und nach Orthostase bei Gesunden und Hypertonikern (1970)
    Springer
    Journal of molecular medicine 48 (1970), S. 598-607 
    Details
    ISSN: 1432-1440
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Summary In 11 of 15 normal subjects, in 7 of 16 patients with essential hypertension and in 6 of 7 with renovascular hypertension plasma renin concentration (PRC) rose significantly after 2 h of orthostasis. In patients with essential hypertension the average increase of PRC is significantly lower than in normal subjects and in patients with renovascular hypertension. The correlation between Δ PRC and Δ RR or Δ Hf is not significant. The PRC increase 90 min after i.v. injection of Furosemide (Lasix-Hoechst) is also smaller in essential hypertension than in normal subjects. In most patients, natriuresis after Lasix is a stronger stimulis of renin secretion than orthostasis. There was no significant difference of the diuretic effect (H2O, Na+, K+) between normotensive and hypertensive subjects, although hematocrit rose less in hypertensives than in normotensives (p=0,05 to 0,1). There is no significant correlation between Δ PRC 90 min after Lasix and Δ Hematocrit, urinary volume or sodium excretion.
    Notes: Zusammenfassung Bei 11 von 15 gesunden Versuchspersonen (gVp.), bei 7 von 16 Patienten mit essentieller Hypertonie (e.H.) und bei 6 von 7 mit renovasculärer Hypertonie stieg die Plasmareninkonzentration (PRC) nach 2 Std Orthostase signifikant an. Der mittlere PRC-Anstieg ist bei der e.H. signifikant geringer als bei den gVp. und den Patienten mit renovasculärer Hypertonie. Wir fanden keine signifikante Korrelation zwischen Δ PRC nach Orthostase und der Änderung von Blutdruck und Pulsfrequenz. Auch der PRC-Anstieg 90 min nach i.v.-Injektion von 80 mg Furosemid (Lasix-Hoechst) ist bei der e.H. signifikant geringer als bei den gVp. Die akute Lasixnatriurese stimuliert die Reninsekretion stärker als 2 Std Orthostase. Wasser-, Natrium- und Kaliumausscheidung nach Lasix waren bei gVp. und e.H. nicht signifikant verschieden. Der Hämatokritanstieg nach akuter Natriurese war bei e.H. geringer als bei gVp. (p=0,05−0,1). Zwischen Δ PRC 90 min nach Lasixgabe einerseits und Δ Hämatokrit, Harnvolumen und Natriumausscheidung andererseits besteht keine signifikante Korrelation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01485393
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  • 3
    Electronic Resource
    Electronic Resource
    Comparative pharmacokinetics of sodium- and methylglucamine diatrizoate in urography (1973)
    Springer
    European journal of clinical pharmacology 6 (1973), S. 137-140 
    Details
    ISSN: 1432-1041
    Keywords: Urography ; Hypaque® ; Urovist® ; pharmacokinetics ; renal failure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Comparative tests were carried out, using a radioactive tracer method, on the pharmacokinetics of sodium and methylglucamine diatrizoate. A biological model was simulated using an analogue computer; and the rate and elimination constants, the elimination half life, and the ratio of tissue entry to tissue elimination constants were calculated. Over the period of time required for X-ray diagnosis, the two salts of the contrast medium acid which were tested did not alter the pharmacokinetics of the contrast medium itself.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00562441
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  • 4
    Electronic Resource
    Electronic Resource
    Tubuloglomerular feedback in rat kidneys of different renin contents (1975)
    Springer
    Pflügers Archiv 359 (1975), S. 33-56 
    Details
    ISSN: 1432-2013
    Keywords: Feedback-Control ; SN GFR ; Early proximal Flow Rate ; Stop Flow Pressure ; Flow Rate through Loop of Henle ; Kidney Renin Content ; Rat Kidney ; Micropuncture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Variations in flow rate through the loop of Henle in the range of 0–50 nl/min were induced using pressure controlled microperfusion. Simultaneously, with the aid of a second pressure-microperfusionsystem, the glomerular function of the same nephron was studied by continuous measurement of two parameters, early proximal flow rate (EPFR) and/or stop flow pressure (SFP). Elevation of loop perfusion above physiological values (40 nl/min) resulted in a drop of EPFR and SFP, whereas lowering perfusion rates had no effect. This feedback behaviour was studied in kidneys with different renin contents to test the role of the renin-angiotensin system in the mediation of the macula densa signal to the adjacent glomerular vessels. Renal renin content, measured after micropuncture experiments by incubation with substrate followed by radioimmunoassay of angiotensin I, was unaltered in control (Ia) and heminephrectomized rats (Ib), lowered in contralateral kidneys of 2 kidneys Goldblatt hypertensive rats (IIa), in DOCA- and salt-loaded rats (IIb), and in DOCA-, salt-loaded and heminephrectomized rats (IIc), and it was elevated in clipped kidneys of Goldblatt hypertension rats (IIIa). Micropuncture evaluation of the tubuloglomerular feedback behaviour in these experimental groups revealed the following results: 1. a feedback response under all conditions independent of the widely varying renin contents (1000-fold), 2. an asymmetrical behaviour of the feedback response in all kidneys as demonstrated by suppression of EPFR and SFP at elevated loop flow rates, but no change of these parameters when loop flow was interrupted, 3. compared to controls the decrease of each GFR parameter between 0 and 40 nl/min loop perfusion was lower in DOCA- and salt-loaded rats (IIb, IIc). Additional heminephrectomy (IIc) had no further influence on the reduced feedback response in DOCA- and salt-loaded rats, whereas this manoeuvre reduced the renal renin content drastically. A somewhat higher response than in controls was found in heminephrectomized rats (IIb) and in clipped kidneys of Goldblatt hypertensive rats (IIIa). These different magnitudes of feedback responses do not correlate with the renal renin content. It has been concluded, therefore, that renal renin activity is not the sole determinant of the effectiveness of the tubuloglomerular feedback response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581276
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  • 5
    Electronic Resource
    Electronic Resource
    Reninabgabe aus Nierenschnitten in Abhängigkeit von der Elektrolytzusammensetzung des Mediums (1970)
    Springer
    Pflügers Archiv 321 (1970), S. 67-82 
    Details
    ISSN: 1432-2013
    Keywords: Renin ; Angiotensin ; Electrolytes ; Kidney Slices ; Rat ; Renin ; Angiotensin ; Elektrolyte ; Nierenschnitte ; Ratte
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Nierenschnitte von Wistarratten wurden in NaCl-Lösungen oder in Ringer-Bicarbonat(bzw. Phosphat-)-Puffern mit 0,1 g Glucose/l für 2 Std bei 37° C aerob inkubiert. 0,1 ml Medium wurde mit 1,9 ml Rinder-Reninsubstratlösung in Anwesenheit von Diisopropylfluorophosphat und EDTA bei pH 5,7 und 37° C für 2 Std inkubiert. Der Angiotensingehalt des Inkubates wurde im Blutdrucktest der Ratte bestimmt. In verschieden konzentrierten NaCl-Lösungen nimmt die Reninabgabe von 150–67 m Val/l (Na+) kontinuierlich ab. Auch in Ringer-Lösungen mit abnehmender NaCl-Konzentration und konstanter Konzentration der übrigen Elektrolyte findet sich zwischen 120 und 50 m Val/l (Na+) ein steiler Abfall der Reninabgabe. Bei Konstanterhaltung der Osmolarität durch zunehmenden Ersatz des NaCl durch Cholinchlorid oder Mannit vermindert sich die Steilheit der (Na+)-Abhängigkeit der Reninabgabe. Ersatz des NaCl im Bicarbonatpuffer durch verschiedene Konzentrationen von NaBr ergibt die gleichen Befunde wie mit NaCl. Bei vollständigem Ersatz des NaCl im Puffer durch verschiedene Konzentrationen von Chlolinchorid oder Mannit ist die Konzentrationsabhängigkeit der Reninabgabe weniger deutlich, bei Ersatz durch KCl nicht mehr signifikant. Die (Na+)-Abhängigkeit der Reninabgabe aus Nierenschnitten scheint nicht vom aeroben Stoffwechsel abhängig zu sein.
    Notes: Summary Rat kidney slices were incubated in saline solutions or in Ringer-bicarbonate (resp. phosphate-)-buffers containing 0.1 g/l glucose for 2 hrs at 37° C. Subsequently, 0.1 ml of the medium was incubated with 1.9 ml of ox renin-substrate solution, pH 5.7, for 2 hrs at 37° C in the presence of diisopropylfluorophosphate and EDTA. The angiotensin formed was measured by rat blood pressure assay. Renin release from kidney slices decreases markedly in NaCl-solutions between Na+-concentrations of 150 meq/l and 67 meq/l. Renin release decreases likewise in modified Ringer-solutions containing decreasing amounts of NaCl or NaBr (between 120 meq/l and 50 meq/l Na+), when the concentrations of other electrolytes are held constant. The (Na+)-dependence of renin release is less marked when the osmolarity of the medium is held constant by stepwise substitution of NaCl cholinchloride. Complete substitution of NaCl by different concentrations of cholin-chloride or mannitol diminishes the dependence of renin release on the osmolarity of the medium. Variation of KCl-concentration in the absence of NaCl does not influence renin release significantly. The (Na+)-dependence of renin release does not seem to depend on aerobic conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00594123
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