Balance between tubular flow rate and net fluid reabsorption in the proximal convolution of the rat kidney

Schnermann, J.; Wahl, Michael; Liebau, G.; Fischbach, H.

doi:10.1007/bf00586722

Cited by 66 publications

(20 citation statements)

References 26 publications

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“…Although not statistically significant, absolute reabsorption increased in experimental rats. This observation is consistent with the findings of Schnermann (14) who reported that during spontaneous variation in glomerular filtration rate in rats the rate of absolute reabsorption varied directly with changes in the filtered load of sodium. To evaluate function in the ascending limb during chronic treatment, clearance studies were performed to measure solute-free water formation during water loading and solute-free water reabsorption during solute loading.…”

Section: Discussionsupporting

confidence: 93%

Effect of Methylprednisolone on Renal Function and the Zonal Distribution of Blood Flow in the Rat

deBermudez

Hayslett

1972

Circulation Research

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The effect of acute and chronic administration of methylprednisolone on renal function was studied in rats with clearance and micropuncture techniques. Although acute administration did not influence renal function, chronic administration for 4 days caused a marked increase in glomerular filtration rate and PAH clearance. The rise in the reabsurption of sodium under these conditions was associated with a disproportionate increase in filtration rate and renal blood flow in deep portions of the cortex. There was no evidence of altered fractional sodium reabsorption in the proximal segment of surface nephrons by micropuncture analysis or in the ascending limb by clearance studies during a water or a solute diuresis.KEY WORDS methylprednisolone sodium reabsorption micropuncture microspheres glomerular filtration PAH clearance proximal tubules• The effect of glucocorticoid hormones on renal function is of importance because of the striking alterations which occur in adrenal insufficiency and the widespread pharmacological use of these agents in patients with intact adrenal function. Previous studies, in the absence of adrenal insufficiency, have suggested that glucocorticoid hormones increase glomerular filtration rate (1, 2) and free water clearance (3, 4) and may influence the tubular reabsorption of sodium (5, 6).In the present study the action of methylprednisolone on sodium reabsorption by the renal tubule was examined in normal rats under conditions of acute and chronic administration by clearance and micropuncture techniques. In addition, since glucocorticoid From the

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Section: Discussionsupporting

confidence: 93%

Effect of Methylprednisolone on Renal Function and the Zonal Distribution of Blood Flow in the Rat

deBermudez

Hayslett

1972

Circulation Research

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“…Within the luminal cell membrane there is a proton ATPase, represented by an empirical expression devised by Strieter et al (37), approximating data of Andersen et al (2) for turtle bladder (33) where J MI (H ϩ ) max is the maximum proton flux and MI (H ϩ ) is the electrochemical potential difference of H ϩ from the cytosol to the lumen; MI defines the steepness of the function, and 0 defines the point of half-maximal activity.…”

Section: Model Formulationmentioning

confidence: 99%

“…IN RESPONSE TO VARIATIONS in glomerular filtration, proximal tubule reabsorption varies proportionally (33), and this glomerulotubular balance derives from both peritubular capillary and luminal factors (14,18,46). Perhaps the most important luminal factor is a direct effect of axial flow velocity on reabsorption (32,56), and along with its impact on sodium reabsorption, luminal flow has been found to influence the transport of glucose (22), bicarbonate (1,8,25), and chloride (15,57).…”

mentioning

confidence: 97%

Flow-dependent transport in a mathematical model of rat proximal tubule

Weinstein¹,

Weinbaum²,

Duan³

et al. 2007

American Journal of Physiology-Renal Physiology

118

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The mathematical model of rat proximal tubule has been extended to include calculation of microvillous torque and to incorporate torque-dependent solute transport in a compliant tubule. The torque calculation follows that of Du Z, Yan Q, Duan Y, Weinbaum S, Weinstein AM, and Wang T (Am J Physiol 290: F289-F296, 2006). In the model calculations, torque-dependent scaling of luminal membrane transporter density [either as an ensemble or just type 3 Na(+)/H(+) exchanger (NHE3) alone] had a relatively small impact on overall Na(+) reabsorption and could produce a lethal derangement of cell volume; coordinated regulation of luminal and peritubular transporters was required to represent the overall impact of luminal flow on Na(+) reabsorption. When the magnitude of torque-dependent Na(+) reabsorption in the model agrees with that observed in mouse proximal tubules, the model tubule shows nearly perfect perfusion-absorption balance at high luminal perfusion rates, but enhanced sensitivity of reabsorption at low flow. With a slightly lower coefficient for torque-sensitive transporter insertion, perfusion-absorption balance in the model tubule is closer to observations in the rat over a broader range of inlet flows. In simulation of hyperglycemia, torque-dependent transport attenuated the diuretic effect and brought the model tubule into closer agreement with experimental observation in the rat. The model was also extended to represent finite rates of hydration and dehydration of CO(2) and H(2)CO(3). With carbonic anhydrase inhibition, torque-dependent transport blunted the diuretic effect and enhanced the shift from paracellular to transcellular NaCl reabsorption. The new features of this model tubule are an important step toward simulation of glomerulotubular balance.

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“…The degree of GTB was often nearperfect, although some deviations from proportionality have been observed during low GFRs (48,50,51). Although GTB in the PCT is a robust and easily demonstrable phenomenon, its explanation has remained a challenge.…”

Section: Proximal Tubule-glomerulotubular Balancementioning

confidence: 99%

Integrated Control of Na Transport along the Nephron

Palmer

Schnermann

2015

Clinical Journal of the American Society of Nephrology

189

143

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The kidney filters vast quantities of Na at the glomerulus but excretes a very small fraction of this Na in the final urine. Although almost every nephron segment participates in the reabsorption of Na in the normal kidney, the proximal segments (from the glomerulus to the macula densa) and the distal segments (past the macula densa) play different roles. The proximal tubule and the thick ascending limb of the loop of Henle interact with the filtration apparatus to deliver Na to the distal nephron at a rather constant rate. This involves regulation of both filtration and reabsorption through the processes of glomerulotubular balance and tubuloglomerular feedback. The more distal segments, including the distal convoluted tubule (DCT), connecting tubule, and collecting duct, regulate Na reabsorption to match the excretion with dietary intake. The relative amounts of Na reabsorbed in the DCT, which mainly reabsorbs NaCl, and by more downstream segments that exchange Na for K are variable, allowing the simultaneous regulation of both Na and K excretion.

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Balance between tubular flow rate and net fluid reabsorption in the proximal convolution of the rat kidney

Cited by 66 publications

References 26 publications

Effect of Methylprednisolone on Renal Function and the Zonal Distribution of Blood Flow in the Rat

Effect of Methylprednisolone on Renal Function and the Zonal Distribution of Blood Flow in the Rat

Flow-dependent transport in a mathematical model of rat proximal tubule

Integrated Control of Na Transport along the Nephron

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