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  • 1
    Electronic Resource
    Electronic Resource
    Effect of dehydration and rapid rehydration on renal function and on plasma renin and aldosterone levels in the black Bedouin goat (1986)
    Springer
    Pflügers Archiv 406 (1986), S. 405-408 
    Details
    ISSN: 1432-2013
    Keywords: Dehydration ; Rehydration ; Kidney functions ; Renin ; Aldosterone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Bedouin goats in the extreme deserts of the Middle East are regularly subjected to severe dehydration and possess a capacity to rapidly rehydrate by drinking large volumes of water. Urine flow, glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) in the fully hydrated animals amounted to 0.74±0.4 ml · min−1, 76±29 ml · min−1 and 344±146 ml · min−1 respectively. In goats that were dehydrated to a loss of about 30% of their initial body weight, urine flow dropped to 24% of the value recorded in the hydrated animals and GFR and ERPF dropped to half their level recorded in the hydrated phase. Na and K+ excretion decreased in the water depleted goats and further decrease was recorded following drinking. Following drinking the urine flow, GFR and ERPF of the recently rehydrated goats dropped to below the rates recorded in the dehydrated animals. During the 3 h of the continuous recording that followed the drinking, all three rates did not exceed the predrinking level. Plasma renin activity amounted to 0.37±0.32 ng AI·ml−1·h−1 in the hydrated animals. In dehydrated ones it amounted to 4.8±2.8 ng AI·ml−1·h−1 and a further increase was recorded following drinking. Aldosterone in the hydrated goats was 5.5±4.3 ng% and increased to 13.9±2.3 ng% in the dehydrated animal and amounted to 20.1±5.5 ng% 2 h following drinking. It is concluded that the kidney in the Bedouin goat plays a major role in conserving both water and solutes, not only when deprived of water but also following its rapid rehydration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00590944
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  • 2
    Electronic Resource
    Electronic Resource
    A sensitive method for determination of renin activity in the single juxtaglomerular apparatus of the rat kidney (1970)
    Springer
    Pflügers Archiv 321 (1970), S. 303-315 
    Details
    ISSN: 1432-2013
    Keywords: Renin ; Juxtaglomerular Apparatus ; Rat Renin Substrate ; Angiotensinase ; Renin ; Juxtaglomerulärer Apparat ; Ratten-Reninsubstrat ; Angiotensinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have established a method for the determination of renin activity in minute amounts of tissue. This method was used for single juxtaglomerular apparatuses (JGA's) of rats. Enzyme kinetic studies were performed to establish the optimal conditions for microdissected JGA's, using purified rat renin and its substrate. Maximal formation of angiotensin occurs at pH 6.5. The effect of incubation and homogenization time, temperature, substrate and renin concentration on the angiotensin formation rate was studied. For the studies reported here purified rat renin substrate was used. The purification methods revealed a substrate content of appr. 1000 ng/mg protein. This highly purified rat renin substrate improved the sensitivity of renin determination in micro amounts of tissue. Hence renin activity of single microdissected JGA's could be quantitatively determined within 1 hour of incubation in a volume of 0.1 ml. Mean renin activity in 18 JGA's from rats kept on standard Altromin diet was 15.2±S.D. 7.0 ng/0.1 ml·hour.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588645
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  • 3
    Electronic Resource
    Electronic Resource
    Sodium entry routes in principal and intercalated cells of the isolated perfused cortical collecting duct (1990)
    Springer
    Pflügers Archiv 416 (1990), S. 88-93 
    Details
    ISSN: 1432-2013
    Keywords: Cortical collecting duct ; Principal cells ; Intercalated cells ; Cell electrolyte concentrations ; Ouabain ; Amiloride ; Na-H exchange ; Electron microprobe analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Transmembrane sodium transport pathways were studied in principal and intercalated cells of the isolated perfused rabbit cortical collecting duct. Intracellular electrolyte concentrations in individual collecting duct cells were measured by electron microprobe analysis during blockage of basolateral Na-K-ATPase by ouabain and simultaneous inhibition of sodium entry across the apical and/or basolateral cell membrane. In principal cells the ouabain-induced rise in cell sodium concentration could only partially be blocked by amiloride (10−4mol/l) in the perfusion fluid. Amiloride (10−3mol/l) added to the bathing solution produced a further, significant reduction of sodium influx. In principal cells the ouabain-induced increase in sodium concentration was completely prevented by amiloride in the perfusion solution in combination with omission of sodium from the peritubular bathing solution. In intercalated cells ouabain caused a less pronounced increase in sodium concentration than in principal cells. Neither amiloride in the perfusate, nor amiloride in both bathing and perfusion solution, significantly reduced the ouabain-induced rise in intercalated cell sodium concentration. These results indicate that in principal cells amiloride-sensitive sodium channels constitute the predominant pathway for sodium entry across the apical cell membrane. In addition, substantial amounts of sodium enter principal cells across the basolateral cell membrane, probably via Na-H exchange. Finally, the data suggest that in intercalated cells sodium channels and the Na-H exchange are sparse or even absent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00370227
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  • 4
    Electronic Resource
    Electronic Resource
    Untersuchungen über die Reaktionsgeschwindigkeit der enzymatischen Angiotensinbildung in vitro in Abhängigkeit von der elektrolytischen Zusammensetzung des Inkubationsmediums (1969)
    Springer
    Pflügers Archiv 310 (1969), S. 137-149 
    Details
    ISSN: 1432-2013
    Keywords: Renin ; Angiotensin ; Enzyme Kinetics ; Ionic Strength ; Renin ; Angiotensin ; Enzymkinetik ; Ionenstärke
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung 1. Die Abhängigkeit der Angiotensinbildungsgeschwindigkeit vom pH, von der Temperatur und von der Konzentration verschiedener Elektrolyte wurde reaktionskinetisch ermittelt. Als Reaktionskomponenten dienten dabei angereichertes Schweineangiotensinogen und homologes Renin. 2. Die Messungen erfolgten unterhalb des Substratsättigungsbereiches in dem anfänglichen, linearen Abschnitt der Michaelis-Menten-Beziehung. 3. Das pH-Optimum der Reaktionsgeschwindigkeit liegt im pH-Bereich 6,0 bis 6,5, das Temperaturmaximum bei 55°C. 4. Als Michaelis-Menten-Konstante wurde ein Wert von 1500 ng Hypertensin Ciba/ml bestimmt. 5. Für NaCl, NaBr, KCl, Na2SO4 und CaCl2 konnte übereinstimmend eine charakteristische Abhängigkeit der Reaktionsgeschwindigkeit von der Ionenstärke mit einem Maximum bei 15–20 mmol gefunden werden. 6. Die Anwesenheit von CdCl2 oder Hg2Cl2 im Inkubationssystem zeigt schon bei niedrigen Molaritäten eine deutliche Hemmung der Angiotensinbildung. 7. Harnstoff, als Nichtelektrolyt, zeigt im Konzentrationsbereich bis 20 mmol ein dem NaCl, KCl usw. analoges Verhalten. Bei höheren Harnstoffgehalten ist, im Gegensatz zu den Elektrolyten, die Geschwindigkeit der Angiotensinbildung nahezu konstant. In physiologischer Kochsalzlösung ist eine Abhängigkeit von der Harnstoffkonzentration nicht mehr zu beobachten.
    Notes: Summary 1. The influence of various electrolytes, pH, and temperature on the reaction velocity for the formation of angiotensin was studied by means of enzyme kinetics. The method involved purified hog renin substrate and hog renin. 2. The steep, linear portion of the Michaelis-Menten curve (below the range of substrate saturation) was used for quantitative analysis. 3. The pH-optimum for the reaction velocity was 6.0–6.5. The temperature maximum was found to be 55°C. 4. The Michaelis-Menten constant had a mean value of 1500 ng Hypertensin Ciba/ml. 5. Reaction velocity rose sharply with increasing concentrations of NaCl, NaBr, KCl, Na2SO4 and CaCl2, reaching a maximum at about 20 mM. Thereafter, there was a gradual decline in reaction velocity with further increase in the concentrations of these electrolytes. 6. CdCl2 and Hg2Cl2 inhibited the reaction velocity throughout the range of concentrations from 0 to 1 mM and 0–66% saturation, respectively. 7. With the non-electrolyte urea, the reaction velocity rose with increasing concentration from zero to about 20 mM. The velocity remained at this maximal value with further increase of the urea concentration to 70 mM. The effect of urea on the reaction velocity was abolished when urea was dissolved in 0.9% NaCl.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00586771
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  • 5
    Electronic Resource
    Electronic Resource
    Transcellular sodium transport and basolateral rubidium uptake in the isolated perfused cortical collecting duct (1993)
    Springer
    Pflügers Archiv 424 (1993), S. 250-254 
    Details
    ISSN: 1432-2013
    Keywords: Cortical collecting duct ; Cell Na+ concentration ; Cell Rb+ uptake ; Na+/K+-ATPase activity ; Principal cell ; Intercalated cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The relation between transcellular Na+ absorption, intracellular Na+ concentration and Na+/K+-ATPase activity (the last estimated by the rubidium uptake across the basolateral cell membrane) was examined in the different cell types of the rabbit cortical collecting duct (CCD). Experiments were performed on isolated perfused CCD in which Na+ absorption was varied by perfusing the tubule with solutions containing different Na+ concentrations (nominally Na+-free, 30 mM and 144 mM). Experiments were terminated by shock-freezing the tubules during perfusion. Precisely 30 s before shock-freezing, the K+ in the bathing solution was exchanged for Rb+. Intracellular element concentrations, including Rb+, were determined in freeze-dried cryosections of the tubules using energy-dispersive X-ray analysis. Increasing Na+ concentration in the perfusion solution caused significant rises in intracellular Na+ concentration and Rb+ uptake of principal cells. Principal cell Na+ and Rb+ concentrations were 7.8±0.9 and 7.0±0.8 mmol/kg wet weight respectively, when the perfusion solution was Na+-free, 10.1±0.7 and 11.6±0.6 mmol/kg wet weight with 30 mM Na+ in the perfusion solution, and 14.5±1.5 and 14.9 ±0.9 mmol/kg wet weight with 144 mM Na+ in the perfusion solution. In contrast, a comparable relationship between lumen Na+ concentration, intracellular Na+ concentration and basolateral Rb+ uptake was not seen in intercalated cells. These results support the notion that principal, but not intercalated, cells are involved in transepithelial Na+ absorption. In addition, the data demonstrate that apical Na+ entry and basolateral Na+/K+-AT-Pase activity are closely coupled in principal cells of the rabbit CCD. A rise in lumen Na+ concentration leads to increased Na+ entry and augmented intracellular Na+ concentration, which then secondarily stimulates active basolateral Na+/K+(Rb+) exchange.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384350
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  • 6
    Electronic Resource
    Electronic Resource
    Effect of ouabain on electrolyte concentrations in principal and intercalated cells of the isolated perfused cortical collecting duct (1989)
    Springer
    Pflügers Archiv 413 (1989), S. 651-655 
    Details
    ISSN: 1432-2013
    Keywords: Cortical collecting duct ; Isolated perfused tubules ; Principal cells ; Intercalated cells ; Cell electrolyte concentrations ; Ouabain ; Electron microprobe analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Sodium, phosphorus, chloride and potassium concentrations were measured by a new method in individual principal and intercalated cells in the cortical collecting duct in vitro. Electron microprobe analysis was applied to freezedried cryosections of the isolated perfused rabbit cortical collecting duct. Cell analyses were performed under control conditions and after addition of ouabain to the bath. Under control conditions similar sodium, potassium, chloride, and phosphorus concentration (means±SEM) were observed in principal (10.0±0.6, 126.5±2.7, 24.6±1.0, and 121.5±3.5 mmol/kg wet weight, respectively) and intercalated cells (9.0±0.9, 127.1±4.2, 27.4±1.8, and 118.7±4.9 mmol/kg wet weight, respectively). In principal cells ouabain (10 min) caused an increase in sodium and chloride concentrations by 104 and 13 mmol/kg wet weight, and a decrease in potassium and phosphorus concentrations by 106 and 32 mmol/kg wet weight. These changes in cell element concentrations can be ascribed to an exchange of intracellular potassium against extracellular sodium and to cell swelling due to influx of extracellular fluid. The effects of ouabain on intercalated cells were far less pronounced than on principal cells. This different susceptibility to ouabain of principal and intercalated cells can be ascribed to differences in active and passive transmembrane ion transport pathways.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581816
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