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- Title
An <em>in vivo</em> study of the concentrating process in the descending limb of Henle's loop.
- Authors
Pennell, J. Phillip; Lacy, Frank B.; Jamison, Rex L.
- Abstract
Two features of the urinary concentrating mechanism were examined in the rat: I) the relative contribution of water extraction and solute addition to the osmolality of fluid in the descending limb of Henle's loop (defined in this paper as that nephron segment beginning at the junction of the cortex and outer medulla), and 2) the difference between the concentration of urea in fluid from the descending limb and from the collecting duct. Rats were studied under three conditions of urinary solute concentration varying from brisk water diuresis to steady-state antidiuresis. Net solute addition contributed substantially (33 to 40%) to the increase in osmolality of descending limb fluid. Urea was the principal solute added: compared to the filtered load, the amount of urea present in fluid at the hairpin turn varied from 334% in water diuresis to 642% in antidiuresis. The differences in urea concentration between fluid from the end of descending limbs and fluid from the tips of collecting ducts (the latter assumed to set an upper limit for interstitial urea concentration) were small, suggesting that the concentration of urea in descending limb fluid approaches equilibrium with that in papillary interstitium. These results are difficult to reconcile with the models recently proposed for generating hypertonicity of the inner renal medulla of the mammalian kidney by passive mechanisms.
- Subjects
UREA; URINALYSIS; BODY fluids; DIURESIS; PHYSIOLOGY; LABORATORY rats
- Publication
Kidney International, 1974, Vol 5, Issue 5, p337
- ISSN
0085-2538
- Publication type
Article
- DOI
10.1038/ki.1974.49