Effect of hyperoncotic albumin on superficial and juxtamedullary nephron sodium transport
Osgood, R.W.; Reineck, H.J.; Stein, J.H.
American Journal of Physiology 237(1): F34-F37
1979
ISSN/ISBN: 0002-9513 PMID: 464058 Document Number: 153947
Previous studies have demonstrated qualitatively similar effects of hyperoncotic albumin and Ringer loading on fractional Na reabsorption along the proximal tubule of superficial nephrons. Urinary Na excretion was significantly greater in the latter setting. Ringer loading results in quantitatively similar inhibition of proximal Na reabsorption in superficial and juxtamedullary nephrons. The effect of hyperoncotic albumin on proximal Na reabsorption was examined in superficial and juxtamedullary nephrons, utilizing delivery to the bend of Henle's loop as an index of this parameter in the latter group of nephrons. Studies were performed in Munich-Wistar rats during hydropenia and after 0.6% body weight hyperoncotic albumin administration. Inulin clearance and fractional Na excretion increased significantly following hyperoncotic albumin administration. During hydropenia, superficial nephron GFR and late proximal Na delivery averaged 25.0 nl/min and 36.8% of the filtered load, respectively. Following hyperoncotic albumin administration, these parameters increased significantly to 36.0 nl/min and 53.8%. Absolute Na reabsorption along the superficial proximal tubule was not affected. In juxtamedullary nephrons, hyperoncotic albumin had no effect on nephron GFR, or fractional or absolute Na delivery to the bend of Henle's loop. Hyperoncotic albumin increases GFR and diminishes proximal fractional Na reabsorption in superficial but not in juxtamedullary nephrons. Absolute reabsorption along the proximal tubule of superficial nephrons is unaltered by hyperoncotic albumin.