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  • 1
    ISSN: 1432-2013
    Keywords: Isolated Rat Kidney ; Electrolyte Transport ; Substrate Dependeney ; Gas Metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We have attempt to define experimental conditions which would overcome or minimize some of the well known functional limitations of isolated single pass kidney preparations. Rat kidneys were perfused with a Krebs-Henseleit solution containing the gelatine derivative Haemaccel as colloid. Perfusion was initiated in situ via the mesenteric artery. Arterial flow rate was measured continously from the very onset of perfusion. Effective perfusion pressure was recorded distal to the perfusion capillary in the aorta. Aliquots of the venous effluate and of an arterial bypass solution were drawn through an O2 electrode for the calculation of $$Q_{{\text{O}}_{\text{2}} } $$ . First it was shown that the often observed initial vasoconstriction of the preparation which occurs immediately after cannulation of the kidney can be eliminated by rapid disconnection of the autonomic nerve supply. A more delayed gradual increase of renal resistance, which we observed after 30 min could be prevented by using sterile perfusion solutions. Using glucose as the only substrate fuel, fractional Na-reabsorption decreased to 65% 3 hrs after the onset of perfusion (T Na=27.3 μEq/g·min). When a substrate enriched sterile solution was used containing pyruvate, lactate, oxaloacetate, and glutamate, Na conservation of the isolated kidney could be maintained at a higher level. Fractional Na-reabsorption levelled off and was still 88% after 3 hrs (T Na=64.4 μEq/g·min). The results demonstrate that the transport function of the isolated kidney preparation critically depends on the supply with substrate hydrogen. Thus, the present system meets the basic reqirements necessary for further micropuncture evaluation of renal function under the condition of isolated single pass perfusion.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2013
    Keywords: Tubular Fluid Reabsorption ; Water Permeability ; Adrenalectomy ; Adrenal Cortical Hormones ; Glucocorticoids ; Tubuläre Flüssigkeitsresorption ; Wasserpermeabilität ; Adrenalektomie ; Nebennierenrindenhormone ; Glucocorticoide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to analyse the mechanism of inhibition of water diuresis in adrenal insufficiency renal surface tubulus of male albino rats (group I: controls, group II: 8 days or more after bilateral adrenalectomy) have been perfused using the free flow microperfusion technique. From the percent osmotic equilibration of a hypotonic perfusate as measured cryoscopically osmotic water permeability (L p) has been calculated. Furthermore, percent osmotic equilibration has been estimated from transtubular net water flux measured with 14C-inulin. With both methods which constitute a maximum estimate (cryoscopic data) and a minimum estimate (inulin data) osmotic water permeability was found to be increased after adrenalectomy in distal convolutions. Hormone substitution with either cortisone (2.5 mg/100 g b.w. 24 hours i.m.) or dexamethasone (0.05 mg/100 g b.w. 24 hours i.m.) reestablished towards normal water permeability after 3 days of treatment. The data are compatible with the concept of a direct effect of glucocorticosteroids on water permeability of distal tubule membranes. In the proximal convolution osmotic water permeability was unaffected by bilateral adrenalectomy.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Using the split oil droplet method the effects of adrenal cortical steroids on impaired renal Na transport have been tested in adrenalectomized white rats. 1. d-aldosterone (dose: 0.125 μg/100 g b.w. intravenously +7.5 μg/100 g b.w. subcutaneously, single dose) after a delay time of about 60 min restored towards normal the local transport capacity for Na of the proximal and distal tubular epithelium. Equal effects were obtained after repeated administration of d-aldosterone (dose: 7.5 μg TMA-aldosterone/100 g b.w. and 24 hrs, intramuscularly) over 3 to 5 days. 2. Similarily, cortisone in high doses (2.5 mg/100 g b.w. intramuscularly as single dose or repeated administration over 3 to 5 days) normalized Na transport capacity in both segments. 3. Dexamethasone, a synthetic steroid with predominant glucocorticoid activity in a dose equivalent to that of cortisone (50 μg/100 g b.w. and 24 hrs intramuscularly as single dose or repeated administration over 3 to 5 days) did not increase the rate of transtubular net Na transport. 4. From the local Na transport capacity and proximal transit time measured with lissamin green fractional NaCl and fluid reabsorption in the proximal convolution has been estimated. Aldosterone, which did not influence proximal transit time, increased fractional reabsorption above control values and above values obtained from adrenalectomized rats without hormone substitution. Fractional reabsorption was normalized by cortisone or was decreased by dexamethasone.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 339 (1973), S. 85-95 
    ISSN: 1432-2013
    Keywords: Blood Pressure Control ; Protein Biosynthesis ; Antibiotics ; Vasoconstrictor Agents ; Magnesium Deficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Antibiotics which inhibit mammalian protein synthesis at different levels were administered intravenously to anesthetized, adrenergic α-receptor blocked rats. 60 sec after cycloheximide application (2.5, 5, 12.5 and 25 μg/100 g body wt), mean arterial pressure increased an average of 4, 19, 25 and 31% respectively. Mean arterial pressure returned to control values after time lapses varying between 5 and 30 min when maximally effective doses were applied. Neither pressure amplitude nor heart rate were significantly altered. Since blood flow measured in a shunt implanted in the lower aorta also did not change, the pressure response to cyclo-heximide is ascribed to an increase in peripheral vascular resistance. The pressor response to cycloheximide could be related to blockade of protein synthesis as puromycin (2.5 mg/100 g body wt), another inhibitor of translation, induced a similar increase of arterial pressure. Actinomycin D (30 μg/100 g body wt) which interferes with RNA synthesis had no acute effect on arterial pressure. Furthermore, the acute effect of cycloheximide is reduced after pretreatment with either actinomycin D, puromycin or cycloheximide. Magnesium deprivation potentiates arterial pressure elevation by cycloheximide and dexamethasone depresses this potentiation. It is postulated that inhibition of protein synthesis at the translation level increases the uptake of contraction triggering calcium by vascular smooth muscle.
    Type of Medium: Electronic Resource
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