ISSN:
1432-2013
Keywords:
Tubular Fluid Reabsorption
;
Tubular Na and K Reabsorption
;
Water Permeability
;
Glucocorticoids
;
Micropuncture Technique
;
Tubuläre Flüssigkeitsresorption
;
Tubuläre Na-und K-Resorption
;
Wasserpermeabilität
;
Glucocorticoide
;
Mikropunktionstechnik
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary In clearance-and micropuncture-experiments the influence of dexamethasone (50 μg/100 g b.w. and 24 hrs intramuscularly over 3 to 5 days) on renal water and electrolyte excretion has been tested in adrenalectomized rats: 1. Glomerular filtration rate, which was reduced in adrenal insufficiency (0.38 ml/min·100 g b.w.) was increased by administration of dexamethasone (0.98 ml/min·100 g b.w.). 2. Water reabsorption, which was increased after adrenalectomy in the proximal convolution (mean endproximal TF/P inulin 5.6) was normalized by dexamethasone (TF/P inulin 3.3). 3. In free flow TF/PNa and TF/PK were close to 1.0 in the proximal convolution of control rats and of dexamethasone-treated adrenalectomized rats. 4. In the second part of the distal tubule of adrenalectomized rats water reabsorption was decreased after dexamethasone below that in control rats (mean TF/Pinulin 11.6 and 18.1 respectively). This difference was not due to a change in fractional K reabsorption. 5. In proximal and distal convolutions 0.9% saline was injected between castor oil and reaspirated after 15–30 sec. In the proximal convolution TF/Posmol, TF/PNa and TF/PK were close to 1.0 in both groups (control rats and adrenalectomized rats after dexamethasone). This was also true for the distal convolution of control rats, indicating an isotonic reabsorption in both segments of control rats.—In contrast, in the distal convolution of dexamethasone-treated adrenalectomized rats the reabsorbate was hypertonic. In the remaining tubular fluid TF/Posmol was 0.78, TF/PNa 0.55 and TF/PK 1.21. These findings agree with microperfusion experiments [25], in which it was demonstrated that dexamethasone lowered the water permeability in the distal convolution. 6. Thus the effect of glucocorticoids on water diuresis in adrenal insufficiency is partly due to an influence of the hormones on GFR and fractional water reabsorption in the proximal convolution, but mainly due to a direct influence on water permeability of the distal tubular epithelium.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00586782
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