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  • 1
    Digitale Medien
    Digitale Medien
    Glomerular tubular balance of renald-glucose transport during hyperglycemia (1980)
    Springer
    Pflügers Archiv 384 (1980), S. 39-47 
    Details
    ISSN: 1432-2013
    Schlagwort(e): d-Glucose ; Tubular Transport ; Glomerulotubular balance ; Micropuncture ; Clearance ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract d-Glucose transport in the kidney of glucose loaded rats was investigated using clearance and micropuncture techniques. The range of plasma glucose concentration in clearance experiments was 20–140 mmol·l−1 and in micropuncture experiments 17–94 mmol·l−1. 1. During hyperglycemia, the glucose concentration in endproximal tubular fluid was elevated above that in arterial plasma. At plasma concentrations above 60 mmol l−1 intratubular glucose concentration was found to be about 1.2 times higher than in plasma. 2. At endproximal puncture sites TF/Posmol was unity throughout the investigated range of hyperglycemia. 3. Proximal tubular glucose reabsorption during hyperglycemia is close to saturation which is compatible to aK m=10.8 mmol l−1 as determined previously. 4. Passive glucose permeability does not change during hyperglycemia. The permeability constant of 2.03·10−5 cm·s−1 does not differ significantly from that during normoglycemia, 1.9·10−5 cm·s−1. 5. Single nephron glomerular filtration rate (SNGFR) and fluid reabsorption in the proximal convolution (C) were significantly correlated during hyperglycemia (r=0.78,P〈0.001). Fractional volume reabsorption during hyperglycemia was decreased to 0.36 as compared to control, but during hyperglycemia it was not affected by the magnitude of the glucose plasma concentration. 6. During hyperglycemia, proximal tubular glucose reabsorption (TG) was correlated to SNGFR (r=0.64,P〈0.001). This relation became insignificant when the influence of volume reabsorption (C) is controlled for (r=0.17,P〉0.5). However, the significance of the correlation between TG and C persists when the influence of SNGFR is held constant. 7. Calculations indicate that when glucose reabsorption was doubled, et sodium transport was increased about fourfold. 8. In hyperglycemia, renal transport rate (TG), when factored by renal glomerular filtration rate (GFR) seems to be linearly related to glucose plasma concentration. Up to endproximal puncture site 25.5% and by the entire kidney 68.2% of the tubular glucose load were reabsorbed. The difference may be attributed either to glucose transport systems which are localized distal to the proximal convoluted tubules and/or to an inhomogenity of the glucose transport in the different types of nephrons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00589512
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  • 2
    Digitale Medien
    Digitale Medien
    Influence of glomerular filtration rate on renal PAH secretion rate in the rat kidney (1978)
    Springer
    Pflügers Archiv 375 (1978), S. 131-139 
    Details
    ISSN: 1432-2013
    Schlagwort(e): PAH clearance ; PAH extraction ; Glomerular filtration rate ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract PAH secretion (TPAH) was studied in rats at spontaneously occurring glomerular filtration rate (GFR). At saturated transport, TPAH was found to be correlated to GFR. This relationship was also observed at unsaturated transport where TPAH depends upon the PAH concentration in arterial plasma. However, no significant correlation between TPAH and renal PAH load or renal plasma flow rate was found when the effects of GFR were removed by partial correlation analysis. A dependency of TPAH on GFR explains the correlations found between filtration fraction (FF) and renal PAH extraction (EPAH) or renal tubular PAH extraction fraction (EPAH-FFPAH). Thus, even at low PAH concentration in a. plasma, renal PAH extraction may only be assumed to be constant if the filtration fraction is constant.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00584235
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  • 3
    Digitale Medien
    Digitale Medien
    Resetting of tubuloglomerular feedback in acute volume expansion in rats (1988)
    Springer
    Pflügers Archiv 411 (1988), S. 322-327 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Tubuloglomerular feedback ; Juxtaglomerular apparatus ; Glomerular filtration rate ; Acute volume expansion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Loss of sensitivity or “resetting” of tubuloglomerular feedback has been reported after both acute and chronic volume expansion in rats. In chronic volume expansion due to dietary salt loading, resetting was found to result from the appearance of an inhibitory factor in tubular fluid. The aim of the present study was to test the possibility that resetting after acute isooncotic volume expansion may also be due to such an inhibitor. Rats were acutely volume expanded (4.5% of body weight) by infusion of a solution of fresh plasma and Ringer's solution. Tubuloglomerular feedback activity was assessed in expanded and control animals by measuring early proximal flow (EPF) rate during perfusion of the loop of Henle at varying rates with proximal tubular fluid harvested from the control (control TF) and expanded animals (AVE TF). When loops of Henle in control animals were perfused with control TF at 10, 20 or 40 nl min−1, EPF fell from (mean ±SD) 29.8±5.6 at zero loop flow to 27.5±7.5, 21.1±4.2 and 15.5±4.5 nl min−1 gKW−1 respectively. Perfusion at the same rates with control TF in expanded animals reduced EPF from 39.5±9.6 (at zero loop flow) to 35.9±11.3, 31.6±4.3 and 22.9±6.8 nl min−1 gKW−1 respectively. When loops of Henle in control animals were perfused with AVE TF, EPF fell from 28.6±9.5 (zero loop flow) to 23.5±8.6, 19.9±8.2 and 15.6±6.5 nl min−1 gKW−1 respectively. Perfusion at these rates with AVE TF in the expanded animals depressed EPF from 36.7±7.8 (at zero loop flow) to 33.6±7.3, 28.6±7.6 and 22.7±8.0 nl min−1 gKW−1 respectively. Since the responses to the two perfusion fluids were the same in each group, it is concluded that there is no inhibitory factor present in AVE TF. Although EPF at each perfusion rate was significantly higher in the expanded animals than in control, the change in EPF per unit change in loop perfusion rate was the same in both groups from which it is concluded that no resetting of tubuloglomerular feedback occurred in the present study.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00585122
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  • 4
    Digitale Medien
    Digitale Medien
    Renal and single-nephron function is comparable in thiobutabarbitone- and thiopentone-anaesthetised rats (1993)
    Springer
    Pflügers Archiv 424 (1993), S. 224-230 
    Details
    ISSN: 1432-2013
    Schlagwort(e): Rat ; Renal function ; Micropuncture ; Blood gases ; Anaesthesia ; Thiopentone ; Thiobutabarbitone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The thiobutabarbitone(TB, Inactin)-anaesthetised rat is an extremely widely used preparation for the study of renal function at the whole-organ and nephron levels. The recent withdrawal of TB from the market has made it essential to find an anaesthetic producing experimental conditions as similar as possible to TB to allow comparison of past and future data. Blood gas analysis, clearance and micropuncture studies were therefore performed in rats anaesthetised with TB or the related thiobarbiturate thiopentone (TP) (both 100 mg/ kg body weight) to establish whether the latter meets this requirement. Both barbiturates caused similar transient respiratory depression and acidosis. Mean values (TP versus TB) over the total 8-h observation period for glomerular filtration rate (0.94 versus 1.05 ml/min), urine flow (3.8 versus 4.4 μl/min) and K+ excretion (0.98 versus 1.18 μmol/min) were slightly lower (P〈0.05) in TP rats, whereas renal blood flow (6.26 versus 6.24 ml/min), filtration fraction (0.31 versus 0.34) and Na+ excretion (0.11 versus 0.098 μmol/min) did not differ. The single-nephron filtration rate (SNGFR) (42.1 versus 41.1 nl/min) and fractional reabsorption (42% versus 47%), both measured in the proximal tubule, did not differ, although in the TP group SNGFR rose with time (4.4%/h) whereas the fractional reabsorption did not change significantly; in the TB group SNGFR was constant but fractional reabsorption declined with time (1.5%/h). Fractional reabsorption up to the distal convoluted tubule declined with time, this was more pronounced in the TP group. SNGFR measured at this site did not differ between TP and TB (30.3 versus 30.1 nl/min) but increased with time with TP (2.7%/h). Although renal function under TP is somewhat less stable than under TB, the differences are minor and, given that the latter is also characterised by non-steady-state conditions, it is concluded that TP is a reasonable replacement for TB.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00384346
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