John W. Boylan

Salt and Water Balance

In warm-blooded animals water makes up about 60 percent of the body weight and exists as a solution of organic and mineral substances. This water is in constant exchange with the environment as a result of periodic uptake from the gut and continual loss through the skin, respiratory passages, and kidney. Within the body the water is distributed in several more or less discrete compartments whose contents are called the “body fluids.” The anatomical boundaries separating these compartments and the differences in the solutes present in each are of fundamental biological significance.

Glucose Reabsorption in the Rat Kidney

ZusammenfassungMit Hilfe der Mikroperfusionstechnik wurde die Glucoseresorption an einzelnen proximalen Tubuli der Rattenniere in situ bei verschiedenen tubulären Perfusionsstromstärken untersucht.1. Bei normalen Glucosekonzentrationen im Plasma gibt es keine nennenswerte Rückdiffusion von Glucose aus dem peritubulären Raum in die Tubulusflüssigkeit, so daß bei der Bestimmung der Glucoseresorptionsrate dieser Faktor zu vernachlässigen ist.2. Eine Änderung der Stromstärke in den perfundierten proximalen Tubulussegmenten führt zu einer gleichsinnigen Änderung der Glucoseresorptionsrate.3. Es besteht dabei eine lineare Korrelation der Glucoseresorptionsrate zur Nettoresorption von Wasser.SummaryGlucose reabsorption was studied at different perfusion rates in the single perfused proximal nephron of the rat. At normal plasma glucose levels diffusion of glucose from peritubular blood to tubular fluid is negligible. Per unit tubular length an increment in glucose reabsorption can be demonstrated with increments in perfusion rate. There is a close correlation between this increment in glucose reabsorption and the net reabsorption of water.

Depletion and restoration of the medullary osmotic gradient in the dog kidney

We have inves t iga ted the deplet ion and res torat ion of the medul la ry osmotie gradient in the dog k idney by slice analysis for sodium and by to ta l osmolar concent ra t ion of t issue wafer. Fou r exper imenta l condi t ions affecting the s teady stare of the medul la ry gradient have been studied : 1. Maximal water diuresis, 2. un i la te ra l nephreetomy, 3. ureteral occlusion and 4. hemorrh~gic hypotension. The reasons for seleeting these eondit ions are discussed below. Sõme observat ions on the magnitude of the gradient between eortex and t ip of papilla as well as between papi l lary t ip and final ur ine have been made.

D-glucose and fluid reabsorption in proximal surface tubule of the rat kidney.

SummaryHexose reabsorption in the kidney was investigated by microperfusion of proximal cortical rat nephrons with Ringers solution containingD-glucose (2.5, 5.0 and 18.0 mM/l), 3-O-methylD-glucose (4.5 mM/l) orD-fructose (18.0 mM/l) at perfusion rates of 20 or 40×10−6 ml/min. Inulin was used as a reference for fluid reabsorption.1.The fraction of fluid reabsorbed was independent of the glucose concentration but it decreased when the perfusion rate increased from 20–40×10−6 ml/min.2.At 18.0 mM/l the % glucose reabsorption was equal to the % fluid reabsorption. This equality was independent of the perfusion rate, (20 or 40×10−6 ml/min), indicating 1:1 coupling with net isotonic fluid reabsorption.3.At 2.5 mM/l the % glucose reabsorption was greater than the % fluid reabsorption, indicating predominance of an active component to theD-glucose transport.4.3-O-methylD-glucose was reabsorbed at one third the rate ofD-glucose. There was no reabsorption ofD-fructose at the concentration used. Since neither of the latter two sugars showed an increment in reabsorption proportional to changes in net fluid movement, we postulate that specificity for glucose reabsorption occurs prior to the site of coupling with fluid flow.

Physiology of the kidney and of water balance

Task of the Kidney.- Morphology of the Kidney.- The Nephron.- Glomerular Filtration.- Gibbs-Donnan Equilibrium.- Correction Factor for Free Solvent.- Filtration Process.- Structure of the Glomerular Filter.- Determination of the Glomerular Filtration Rate.- Tubular Transport.- Micropuncture Methods.- The Intratubular Methods.- Solute Transport Through the Tubular Cells.- Electrophysiology of the Nephron.- Electrolyte Transport.- Energy Metabolism of the Kidney.- Ultrastructure of the Nephron.- Trans-tubular Water Flux.- Peritubular Factors Affecting Reabsorption.- Effect of Aldosterone on the Nephron.- Calcium Reabsorption in the Kidney.- Tubular Transport of K+ in the Kidney.- Reabsorption of Glucose in the Kidney.- Phosphate Reabsorption in the Kidney.- Sulfate Reabsorption in the Kidney.- Reabsorption of Amino Acids in the Kidney.- Uric Acid Transport.- Reabsorption of Protein in the Kidney.- Transport of Urea.- Reabsorption of Bicarbonate in the Kidney.- Mechanisms of Bicarbonate Transport.- Hydrogen Ion Transport.- Secretion of Hydrogen Ions.- Excretion of Hydrogen Ions.- Excretion of Titratable Acid.- Excretion of Ammonia.- Secretion of Organic Acids.- Specificity of the Transport System for Organic Acids.- Non-Ionic Diffusion.- Renal Extraction.- Measurement of Renal Plasma Flow.- Renal Hemodynamics.- Magnitude of the Renal Blood Flow.- Vascular Anatomy of the Kidney.- Localization of the Renal Vascular Resistance.- Regulation of Renal Blood Flow.- The Arterio-Venous Oxygen Difference Across the Kidney.- The Intrarenal Distribution of Blood Flow.- Medullary Blood Flow.- Urine-Concentrating Mechanism.- Importance of the Medulla.- Principle of a Counter-Current Multiplier.- Experimental Evidence for the Counter-Current System.- The Modus Operandi of the Counter-Current System in the Kidney.- Role of Urea in the Concentrating Process81.- Significance of the Medullary Blood Flow in Relation to Concentrating Ability.- Counter-Current Diffusion.- Significance of the Urine-Concentrating Mechanism.- Water Diuresis and the Effect of Antidiuretic Hormone (ADH).- Evolution of the Kidney.- References.- Salt and Water Balance.- Water as the Basis of Life.- Solvent Properties of Water.- Thermal Properties of Water.- Neutrality and Ionization Constant.- Input and Output of Water.- Water Absorption from the Gut.- The Body Fluids.- Composition and Ionic Content of the Body Fluids.- Volume Regulation in the Fluid Compartments and Sodium Balance.- Survival in Conditions of Water Shortage.- Physiological Effects of Dehydration.- Survival at Sea.- Desalination of Sea Water for Drinking Purposes.- Water Supplies in Outer Space.- References.

Renal clearance in the unanesthetized guinea pig: depression of inulin clearance by creatinine.

Summary Renal function studies were conducted in unanesthetized guinea pigs. 1. The mean value for inulin clearance obtained compares satisfactorily with published data in other small mammals. Inulin clearance is independent of plasma concentration over a wide range of U/P ratios and independent of urine flow except at very low flow rates, when it is depressed. 2. A ratio of endogenous creatinine to inulin clearances of 0.95 indicates that in the guinea pig, endogenous creatinine clearance is a measure of glomerular filtration rate. 3. The average ratio of urea to inulin clearance obtained here (0.61) agrees well with the established figure for most mammals. 4. Inulin and urea clearances were consistently reduced by prior administration of creatinine. The mechanism of this reduction is beyond the scope of this study. 5. The clearance of exogenous creatinine is greater than that of endogenous creatinine. This, with the foregoing, suggests that in this species there is a tubular component in excretion of exogenous creatinine.