SUMMARY1. Short loops of Henle were artificially perfused with saline solutions containing 5 or 0 mM-glucose in the presence and absence of phlorizin.2. Net fluid reabsorption was greater when glucose but no phlorizin was present than in all other series.3. Glucose was reabsorbed from glucose-containing perfusate and this was abolished by phlorizin. Secretion of glucose occurred into the perfusate which initially contained no glucose and this secretion was enhanced by phlorizin.4. Sodium reabsorption was inhibited by phlorizin when glucose was present, but enhanced by phlorizin when glucose was absent.5. It can be shown that there is secretion of some osmotically active solute in all series. Its secretion is enhanced by phlorizin in the absence of glucose.

SUMMARY1. The effect of phlorizin on glucose, water and sodium handling by the kidney in anaesthetized rats was investigated, using clearance techniques, during infusion of saline (200 j1. min-') or saline to which either low (0 1 smole kg body weight-' ml.-') or high (1.0 molee kg body weight-' ml.-') doses of phlorizin had been added.2. Phlorizin increased the absolute and fractional excretion of glucose, urine osmolality and negative free water clearance; and reduced urine flow rate, glomerular filtration rate (GFR), absolute and fractional excretion of sodium, absolute excretion of sodium, absolute excretion of potassium and absolute and fractional rates of glucose reabsorption.3. The data indicate that phlorizin has sites of action and effects additional to those on glucose transport in the proximal tubule.4. Within each series there was a positive correlation between sodium and glucose reabsorption; but the rate of glucose reabsorption was different between each series even though the sodium reabsorption was not.5. It is suggested that since both sodium and glucose reabsorption correlate with GFR, they may be related via GFR.6. The data indicate that for the whole kidney any effect of glucose on sodium transport is small relative to total renal handling of sodium.