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Experiments were performed on 23 dogs to assess the effect of splanchnic pooling on renal hemodynamics and Na retention. When the thoracic duct pressure was raised to 40 cm H2O (HTDP), liver interstitial pressure rose from 9.0 +/- 0.4 to 19.8 +/- 1.1 cm H2O. Simultaneously, glomerular filtration rate (GFR) and renal plasma flow fell in the left kidney from 16.3 +/- 1.7 to 9.6 +/- 1.3 and from 73.7 +/- 12.2 to 44.3 +/- 9.8 ml.min-1, respectively (p less than 0.01). UNa.V fell to 59 +/- 9% of control value (p less than 0.01). Plasma antidiuretic hormone (ADH) rose from 29.5 +/- 7.7 to 46.9 +/- 9.2 pg.ml-1 (p less than 0.05). When a portocaval shunt (PCS) was opened in 10 dogs during HTDP after the first set of experimental measurements, splanchnic pressure fell from 17.2 +/- 1.1 to 11.5 +/- 1.2 cm H2O, attended by a return towards control of GFR. ADH fell significantly to 16.5 +/- 8.1 during PCS, and to 9.7 +/- 1.5 pg.ml-1 during a last, postexperimental control period. Instead, UNa.V remained unchanged at the low levels measured during HTDP alone. When the HTDP was released in the 17 dogs without, and the 10 dogs with PCS, all variables became indistinguishable from control, except for UNa.V, which remained reduced, even in 4 aldosterone-escaped animals. No significant change in any of these variables occurred in 6 sham-operated control animals. These data demonstrate that it is possible to increase interstitial liver pressure through the lymph duct.(ABSTRACT TRUNCATED AT 250 WORDS)

In a previous study, we described a new method [3] to measure Na reabsorption by each segment of the human nephron independently. Reabsorption was expressed as equivalent volumes of solute-free water (CH2O) generated by the loop of Henle (CH2O-HL) and by the distal tubule (CH2O-DT), and dissipated by back diffusion (BD) across collecting ducts (CH2O-BD). These data were obtained during maximal water diuresis (MWD). The present study was undertaken to calculate CH2O-HL by experiments performed during maximal antidiuresis (MA). For this purpose, a new theoretical approach was devised, described by algebraic equations which allowed calculations of segmental transport during MA alone, where only CH2O-HL could be calculated independently. The study was performed on 14 normal volunteers who were studied twice by clearance measurements, firstly during MWD and again during MA. In each experiment, clearance periods were performed during baseline conditions and during the administration of furosemide (0.7 mg/kg bolus injection followed by 0.06 mg/kg/min maintenance infusion). From the values measured during either condition, segmental reabsorption was calculated. During MWD, CH2O-HL averaged 19.4 + 10.4, during MA 20.4 + 8.0 ml/min/GFR X 100; p greater than 0.05. The paired measurements were significantly correlated (r = 0.80; p less than 0.01). These data demonstrate that CH2O-HL obtained with the original theory is a reproducible result that can be confirmed with independent measurements obtained during different experimental conditions. Thus, measurements of segmental Na transport in the human nephron are feasible and can contribute important informations on disease states.

The segment of the nephron where carbohydrate deprivation depresses Na transport leading to natriuresis was sought by a new clearance technique designed to measure segmental reabsorption in each portion of the human renal tubule. Experiments were performed during maximal water diuresis before and 4 days after carbohydrate withdrawal. Proximal reabsorption had fallen from 70 +/- 4 to 60 +/- 5 ml X min-1, p less than 0.05, by the 4th day of sugar deprivation, accounting for the natriuresis and the associated weight loss of 1.8 kg. By the 4th day of fasting, when Na excretion had returned to control levels, GFR had fallen nonsignificantly from 99 +/- 6 to 95 +/- 5 ml X min-1, while Na reabsorption along distal segments had risen. In fact, Na transport, expressed by the equivalent volumes of solute free-water generated, rose from 17.4 +/- 3.4 to 23.6 +/- 2.1 along the ascending limb of Henle's loop, and from 8.1 +/- 0.8 to 9.2 +/- 1.3 ml X min-1 X GFR-1 X 100 along the distal tubule. Thus, analysis of segmental Na transport by this method discloses that starvation natriuresis is a proximal tubular event, progressively counterbalanced by enhanced Na reclamation in more distal sites. Volume contraction and the attendant fall in GFR concur to curb delivery out of the proximal tubule which is matched by enhanced distal Na reabsorption till a new steady-state excretion is attained.

A 17-year-old male patient with Bartter's syndrome was admitted for renal function studies. This patient had persistent hypokalemia, first found at age 5; the diagnosis of Bartter's syndrome with renal hypersecretion of prostaglandins E2 and F2 alpha had been established at age 13. A congenital defect of chloride reabsorption was expected, but after 4 years of indomethacin treatment no such defect was found. Withdrawal of indomethacin for 1 week resulted in profound hypokalemia and the appearance of a chloride reabsorption defect, with an excessive urinary PGE2 and PGF2 alpha excretion, and a parallel decrease in plasma prostaglandin precursors. The cause of Bartter's syndrome in this patient seems to be renal hyperprostaglandinism.