The hydraulic conductivity of the rat proximal tubular wall determined with colloidal solutions

Persson, A. Erik G.; Schnermann, J.; Ågerup, Bengt; Eriksson, Nils-Einar

doi:10.1007/bf00584324

Cited by 12 publications

(7 citation statements)

References 35 publications

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“…The principle argument against a direct effect of protein across junctional complexes is the observation that addition of protein to the luminal solution does not influence Jv (7,8,49). Other studies (12,50), however, find that luminal protein dramatically inhibits J,. Second, protein might influence the passive component of anion gradient-dependent NaCl transport (10,11).…”

Section: Discussionmentioning

confidence: 99%

Influence of peritubular protein on solute absorption in the rabbit proximal tubule. A specific effect on NaCl transport.

Berry¹,

Cogan²

1981

J. Clin. Invest.

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A B S T R A C T The effect of removal of peritubular protein on the reabsorption ofvarious solutes and water was examined in isolated rabbit proximal convoluted tubules (PCT) perfused in vitro. In 22 PCT perfused with ultrafiltrate (UF) and bathed in serum, volume absorption (JV) was 1.44 nl/mm per min and potential difference (PD) was -3.6 mV. When these same PCT were bathed in a protein-free UF, JV was reduced 38% without a change in PD. Simultaneous measurements of total CO2 net flux (JTCO2) and glucose efflux (JG) showed that <2% of the decrease in JV could be accounted for by a reduction in JTCO2 and JG, suggesting that removal of peritubular protein inhibited sodium chloride transport (JNacl). Therefore, in eight additional PCT, JNaCl was measured, in addition to PD, JV, JG, and JTCO2. In these PCT, the decrease in total solute transport induced by removal of bath protein was 201.7±37.5 posmol/mm per min. JG decreased slightly (9.1±3.9 posmol/mm per min); NaHCO3 transport did not change (9.2±6.6 posmol/mm per min); but JNac1 decreased markedly (160.6±35.7 posmol/mm per min). 80% of the decrease in JV could be accounted for by a decrease in JNacl. In 13 additional PCT perfused with simple NaCl solutions, a comparable decrease in JV and JNaci was observed when peritubular protein was removed without an increase in TCO2 backleak.

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Section: Discussionmentioning

confidence: 99%

Influence of peritubular protein on solute absorption in the rabbit proximal tubule. A specific effect on NaCl transport.

Berry¹,

Cogan²

1981

J. Clin. Invest.

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“…This view is best supported by data showing that addition of luminal protein dramatically inhibited volume absorption in the rat PCT (7,8). Other studies (9,10) in both the rat and the rabbit PCT, however, find that luminal protein does not influence volume absorption.…”

Section: Effect Of Peritubular Protein Removal On (Rm)mentioning

confidence: 92%

“…Data relating to this hypothesis have been conflicting. Some studies report that protein added to the luminal perfusate inhibits spontaneous volume absorption (7,8), whereas other studies have failed to show an effect of luminal protein (9,10).…”

mentioning

confidence: 99%

Lack of effect of peritubular protein on passive NaCl transport in the rabbit proximal tubule.

Berry¹

1983

J. Clin. Invest.

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A B ST R A CT The effect of peritubular protein removal on passive NaCi transport was examined in the isolated rabbit proximal convoluted tubule (PCT). Three modes of passive NaCl transport were tested: (a) paracellular backflux of NaCl, (b) convective flow of NaCl through junctional complexes, and (c) anion gradient-dependent NaCl transport. The effect of peritubular protein removal on the paracellular permeability to NaCl was examined using transepithelial specific resistance. Eight PCT were perfused with ultrafiltrate (UF) and bathed in either serum or UF. Transepithelial specific resistance averaged 14.5±1.9 in the presence and 13.7±1.7 f cm2 in the absence of peritubular protein. The effect of peritubular protein removal on the convective flow of a NaCl solution across junctional complexes was examined in the absence of active transport by using colloid osmotic pressure (COP) gradients. 12 PCT were perfused with simple salt solutions in Donnan equilibrium with and without protein at 20'C. A COP gradient of 60.1 and -60.1 mmHg drove only 0.06 and -0.23 nl/min, respectively. These values are -10% of the value predicted for an effect of peritubular protein on NaCl solution flow (1.98 nl/min) and are approximately equal to the value predicted for pure water equilibration for the small osmotic pressure difference between solutions in Donnan equilibrium (0.17-0.18 nl/min). The effect of peritubular protein removal on the passive absorption of NaCl driven by anion concentration gradients was examined in seven PCT perfused with a high chloride solution simulating late proximal tubular fluid and bathed in either serum or UF at 20'C. Volume absorption averaged 0.34±0.20 in the presence and 0.39±0.20 nl/mm min in the absence of peritubular protein. In conclusion, peritubular protein removal did not significantly affect any of the three distinct modes of passive NaCl transport tested. The

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“…A significant combined hydrostatic and oncotic pressure difference across the proximal tubular wall has been found (Wolgast et al 1973, Wunderlich et al 1971. A high hydraulic conductance in the proximal tubular wall has also been found (Persson et al 1975, Schafer et al 1978. From these determinations we have estimated that 30 % of total transepithelial fluid transport across the proximal tubular wall is driven by the physical forces.…”

mentioning

confidence: 80%

Modulation of proximal tubular hydraulic conductivity by peritubular capillary oncotic pressure

Ågerup

1982

Acta Physiologica Scandinavica

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Fluid absorption from the proximal tubular lumen is probably a multifactorial process. Earlier studies from our laboratory have indicated that a transepithelial hydrostatic and oncotic pressure difference may be the driving force for as much as 30% of the reabsorbed fluid. During saline volume expansion proximal tubular reabsorption declines and the present experiments were undertaken to investigate whether this reduction could be caused by changes in the passively driven flux component. The hydraulic conductivity was therefore determined from the reabsorptive rate in split oil droplets with normal and high hydrostatic pressure gradients across the wall, at the same time as the peritubular capillary net-work was perfused with solutions containing a colloid of high or low concentration. In the reabsorption experiments the split oil droplet radius was measured and in a separate series of experiments the relationship between droplet radius and pressure was determined; this was found to be 7.3 mmHg pressure increase per 1 micrometer increase in radius. The increase in the rate of reabsorption from the droplets due to increased intraluminal hydrostatic pressure was 1.02 +/- 0.13 nl/min/mm tubular length when a solution with a high colloid concentration was perfused through the capillary net-work, compared with 0.41=0.11 nl/min/mm tubular length when a low colloid containing solution was used for perfusion. The hydraulic conductance in the proximal tubular wall at high colloid perfusion was calculated to be 0.54 nl/min.mm.mmHg while at a low capillary colloid oncotic pressure it was significantly lower 0.025 nl/min.mm.mmHg. This drop in hydraulic conductance might be one factor responsible for the decline in fluid absorption in animals exposed to saline volume expansion.

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The hydraulic conductivity of the rat proximal tubular wall determined with colloidal solutions

Cited by 12 publications

References 35 publications

Influence of peritubular protein on solute absorption in the rabbit proximal tubule. A specific effect on NaCl transport.

Influence of peritubular protein on solute absorption in the rabbit proximal tubule. A specific effect on NaCl transport.

Lack of effect of peritubular protein on passive NaCl transport in the rabbit proximal tubule.

Modulation of proximal tubular hydraulic conductivity by peritubular capillary oncotic pressure

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