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Abstract
Micropuncture of the proximal convoluted tubule during mannitol diuresis in rats in
poor physiologic condition because of abdominal exposure of the kidney disclosed that
steep potassium concentration gradients between tubular fluid and plasma could be
generated, with concentration ratios as low as 0.5. This constitutes definitive evidence
that proximal tubular potassium reabsorption must be active, since a passive process
mediated by solvent drag could not depress the luminal concentration of potassium.
Similar studies during mannitol diuresis in rats in good physiologic condition (flank
exposure of the kidney) revealed that the proximal tubule, under these conditions,
did not generate steep concentration gradients; the concentration ratios were the
same as in nondiuretic rats (0.9); moreover, urinary potassium excretion rose linearly
as urine mannitol diuresis mounted. These findings establish that in this group potassium
reabsorption was sharply depressed by mannitol diuresis and suggest that the increased
urinary potassium excreted by these rats may have been derived from the filtered potassium
which escaped proximal reabsorption.
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References
- The Mechanism of Potassium Reabsorption in the Proximal Tubule of the Rat.J. Clin. Invest. 1963; 42: 277
- Ultramicro Determination of Potassium and Sodium in Biologic Fluids.J. Lab. & Clin. Med. 1963; 61: 692
- Micropuncture Study of Renal Tubular Transfer of Sodium Chloride in the Rat.Am. J. Physiol. 1961; 200: 581
Rector, F. C., Jr.: Unpublished observations.
- Evidence for a Direct Effect of Serum Sodium Concentration on Sodium Reabsorption.J. Clin. Invest. 1962; 41: 850
- The Effect of Hypertonic Solutions on the Metabolism and Excretion of Electrolytes.Am. J. Physiol. 1949; 159: 160
- Renal Mechanisms for Potassium Excretion.in: ed. 3. The Harvey Lectures, Series 55. Academic Press, Inc, New York1961: 141
Article info
Publication history
Accepted:
September 25,
1963
Received:
July 18,
1963
With the technical assistance of MARTHA HUDDLESTONFootnotes
☆Supported in part by grant HTS-5469 from the National Institutes of Health and in part by a grant from the Dallas Heart Association.
Identification
Copyright
© 1964 Published by Elsevier Inc.
