Actions of Frusemide and a Thiazide

Use of Furosemide for Evaluation of the Urinary Concentrating Mechanism in Chronic Pyelonephritis

“…3). Similar changes have been observed by us in patients with psychogenic polydipsia (16) and diabetes insipidus due to ADH deficiency without renal disease (17). It should be emphasized that the studies were made after pretreatment with a "maximal" dose of hydrochlorothiazide, i.e., in the presence of blocked free water formation (inhibited sodium reabsorption) in the cortical diluting segment of the distal nephron (18).…”

“…The lack of accumulation of a high solute content may be due to insufficiency of active sodium transport in the ascending limb of the loop of Henle and/or loss of the "trapping" function of the renal medulla. We attempted to make a distinction between these theoretical possibilities in our case by using furosemide, a diuretic which inhibits sodium reabsorption in the loop of Henle (15)(16)(17).…”

“…It should be emphasized that the studies were made after pretreatment with a "maximal" dose of hydrochlorothiazide, i.e., in the presence of blocked free water formation (inhibited sodium reabsorption) in the cortical diluting segment of the distal nephron (18). Thus it was possible to demonstrate that the decrease of free water clearance induced by furosemide did not occur in the cortical diluting segment but in the medullary diluting segment, i.e., in the ascending limb of the loop of Henle (15)(16)(17)(18). This interpretation is supported also by the further decrease of the initially low reabsorption of free water in response to furosemide during the infusion of hypertonic sodium chloride solution in hydropenia ( Table 2 and Fig.…”