Micropuncture study of renal tubular transfer of sodium chloride in the rat

Abstract

Micropuncture studies were made in the rat on the relationship between net water and net sodium movement across proximal tubular epithelium during strong osmotic diuresis induced by intravenous infusion of a 20% mannitol solution. Results obtained in the mannitol series were compared with data obtained in rats during infusion of 0.9% saline. Collected tubular fluid and appropriate plasma samples were analyzed for C14 inulin or creatinine, chloride and radiosodium. The latter was injected intravenously several hours prior to tubular puncture. Net water reabsorption across the proximal tubule was less than under nondiuretic conditions. The concentration of radiosodium and of chloride in proximal tubular fluid was found to be below that of plasma in osmotic diuresis. Much steeper gradients for these ions were found across distal tubular epithelium indicating that parts other than the proximal convolution participate in the establishment of the over-all concentration gradients. Since net sodium movement occurred against an electrochemical potential gradient during osmotic diuresis, this study provides evidence for active transport of sodium ions across the proximal tubular wall.

Effects of water diuresis and osmotic (mannitol) diuresis on urinary solute excretion by the conscious rat

“…Hypertonic mannitol would be expected to stimulate or sustain endogenous A.D.H. production (Windhager & Giebisch, 1961). In the presence of A.D.H., the collecting duct wall is permeable to urea (Jaenike, 1961; Thomas, 1964;Foulkes, 1966), allowing passive diffusion into the nephron during the generation of the diuresis if the collecting duct fluid urea concentration fell more rapidly than that of the medullary interstitium.…”

A Microperfusion Study of Phsophate Reabsorption by the Rat Proximal Renal Tubule EFFECT OF PARATHYROID HORMONE

“…Y.) for measurement of volume (24), and were then washed into liquid scintillation vials for radioactive counting in a Nuclear-Chicago counter, Unilux II A (Nuclear-Chicago Corp., Des Plaines, Ill.). Separation of the two isotopes was almost complete.…”

Micropuncture Study of Inorganic Phosphate Excretion in the Rat *

“…Normal and phosphate-loaded animals, weighing 300 to 450 g, were studied. The technique of preparing the animals for micropuncture, tubular fluid sampling, and localization of the puncture site have previously been described in a paper from this laboratory (23). Purina lab chow (calcium 1.42%, phosphate, 0.96%) was available to both groups of animals until 15 to 18 hours before an experiment.…”

“…C" carboxyl inulin was estimated in a Tri-Carb liquid scintillation spectrometer 4 as previously described (23).…”