The relationship between peritubular capillary protein concentration and fluid reabsorption by the renal proximal tubule.

The relationship between peritubular capillary protein concentration and rate of sodium reabsorption by the rat proximal tubule was examined using free-flow recollection micropuncture techniques. Tubule fluid-to-plasma inulin ratios were measured before, during, and at successive intervals after brief (15-25 sec) intra-aortic injections (at the level of the renal artery) of colloid-free, isoncotic, and hyperoncotic solutions. Arterial hematocrit and protein concentrations were measured simultaneously in these rats. In other rats, total protein concentration of peritubular capillary blood plasma was determined before, during, and after these same infusions with a newly described submicroliter fiber-optic colorimeter. In the 15-25 sec interval necessary to infuse 2 ml of these test solutions, fractional and absolute sodium reabsorption varied directly with peritubular capillary colloid osmotic pressure, declining during infusion of colloid-free solutions, increasing during hyperoncotic infusions, and remaining unchanged during isoncotic infusions. In the subsequent 20-min interval after intra-aortic injection of these test solutions, capillary protein concentration remained at (isoncotic infusions) or returned to (colloid-free and hyperoncotic fluids) control values. Whereas reabsorption after colloid-free solutions returned to base line levels in parallel with the return in capillary protein concentration, after colloid infusions (which resulted in continued expansion of extracellular fluid volume), a progressive decline in reabsorption was observed. These results afford strong evidence that peritubular capillary colloid osmotic pressure is one important determinant of proximal sodium reabsorption. Nevertheless it is apparent that mechanisms other than or in addition to this must be invoked to explain the delayed inhibition of reabsorption that accompanies expansion of extracellular fluid volume by colloid solutions.

[1]  B. Brenner,et al.  Relationship between extracellular volume and fluid reabsorption by the rat nephron. , 1969, The American journal of physiology.

[2]  F. S. Wright,et al.  Failure to demonstrate a hormonal inhibitor of proximal sodium reabsorption. , 1969, The Journal of clinical investigation.

[3]  R L Bowman,et al.  Fiber-optic colorimeter for submicroliter samples. , 1969, Analytical biochemistry.

[4]  J. Orloff,et al.  Control of fluid absorption in the renal proximal tubule. , 1968, The Journal of clinical investigation.

[5]  J. A. Martino,et al.  Relationship between Intrarenal Hydrostatic Pressure and Hemodynamically Induced Changes in Sodium Excretion , 1968, Circulation research.

[6]  F. S. Wright,et al.  Depression of fractional sodium reabsorption by the proximal tubule of the dog without sodium diuresis. , 1968, The Journal of clinical investigation.

[7]  B. Brenner,et al.  The relationship between glomerular filtration rate and sodium reabsorption by the proximal tubule of the rat nephron. , 1968, The Journal of clinical investigation.

[8]  E. Windhager,et al.  Peritubular control of proximal tubular fluid reabsorption in the rat kidney. , 1968, The American journal of physiology.

[9]  F. Rector,et al.  Demonstration of a hormonal inhibitor of proximal tubular reabsorption during expansion of extracellular volume with isotonic saline. , 1968, The Journal of clinical investigation.

[10]  J. A. Martino,et al.  Demonstraton of a role of physical factors as determinants of the natriuretic response to volume expansion. , 1967, The Journal of clinical investigation.

[11]  F. S. Wright,et al.  Cross‐Circulation Experiments on the Mechanism of the Natriuresis during Saline Loading in the Dog , 1967, Circulation research.

[12]  N. Levinsky.  NONALDOSTERONE INFLUENCES ON RENAL SODIUM TRANSPORT * , 1966, Annals of the New York Academy of Sciences.

[13]  J. A. Martino,et al.  Factors affecting sodium reabsorption by the proximal tubule as determined during blockade of distal sodium reabsorption. , 1966, The Journal of clinical investigation.

[14]  G. G. Vurek,et al.  Fluorometric method for the determination of nanogram quantities of inulin , 1966 .

[15]  J. O. Davis,et al.  Evidence from Gross Circulation Studies for a Humoral Mechanism In the Natriuresis of Saline Loading , 1966, Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine.

[16]  F. Rector,et al.  Mechanism of glomerulotubular balance. I. Effect of aortic constriction and elevated ureteropelvic pressure on glomerular filtration rate, fractional reabsorption, transit time, and tubular size in the proximal tubule of the rat. , 1966, The Journal of clinical investigation.

[17]  F. Rector,et al.  Mechanism of glomerulotubular balance. II. Regulation of proximal tubular reabsorption by tubular volume, as studied by stopped-flow microperfusion. , 1966, The Journal of clinical investigation.

[18]  L. Earley,et al.  The effects of combined renal vasodilatation and pressor agents on renal hemodynamics and the tubular reabsorption of sodium. , 1966, The Journal of clinical investigation.

[19]  P. Vereerstraeten,et al.  Réduction de la natriurèse par la perfusion de protéines dans l’artère rénale du chien , 1966 .

[20]  L. Earley,et al.  Studies on the mechanism of natriuresis accompanying increased renal blood flow and its role in the renal response to extracellular volume expansion. , 1965, The Journal of clinical investigation.

[21]  L. Earley,et al.  CHANGES IN RENAL BLOOD FLOW AND POSSIBLY THE INTRARENAL DISTRIBUTION OF BLOOD DURING THE NATRIURESIS ACCOMPANYING SALINE LOADING IN THE DOG. , 1965, The Journal of clinical investigation.

[22]  F. Epstein,et al.  Effect of Protein in Tubular Fluid upon Proximal Tubular Absorption.∗ , 1964, Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine.

[23]  G. Giebisch,et al.  Sodium Movement across Single Perfused Proximal Tubules of Rat Kidneys , 1964, The Journal of general physiology.

[24]  G. Giebisch,et al.  RENAL TUBULAR TRANSFER OF SODIUM, CHLORIDE AND POTASSIUM. , 1964, The American journal of medicine.

[25]  R. B. Kelman.  A theoretical note on exponential flow in the proximal part of the mammalian nephron. , 1962, The Bulletin of mathematical biophysics.

[26]  I. Mills,et al.  Studies on the efferent mechanism of the sodium diuresis which follows the administration of intravenous saline in the dog. , 1961, Clinical science.

[27]  E. Bresler.  The problem of the volume component of body fluid homeostasis. , 1956, The American journal of the medical sciences.

[28]  G. Vogel,et al.  Versuche zur Bedeutung kolloidosmotischer Druckdifferenzen für einen passiven Transportmechanismus in den Nierenkanälchen , 1955 .

[29]  O. H. Lowry,et al.  Protein measurement with the Folin phenol reagent. , 1951, The Journal of biological chemistry.

[30]  J. Barcroft,et al.  The Secretion of the Urine , 1910, Nature.