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

deBermudez, Lidia; Hayslett, John P.

doi:10.1161/01.res.31.1.44

Cited by 55 publications

(24 citation statements)

References 18 publications

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“…This is consistent with recent reports that methylprednisolone had no effect on sodium or water reabsorption in the kidney (33,34). However because only three studies were performed it is not possible to be certain that the glucocorticoids chronically administered did not cause some increase in the capacity to reabsorb sodium in the diluting sites, thus perhaps somewhat diminishing the effect of saline.…”

Section: Methodssupporting

confidence: 91%

Effect of Extracellular Volume Expansion upon Sodium Reabsorption in the Distal Nephron of Dogs

Bennett¹

1973

J. Clin. Invest.

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A B S T R A C T Micropuncture studies have disclosed that extracellular fluid (ECF) volume expansion inhibits sodium reabsorption in the proximal tubule. The diuresis that ensues represents only a portion of the increment in sodium and water escaping proximal reabsorption, since a large and variable fraction of the increment is reabsorbed distally. In certain experimental models proximal reabsorption may be depressed by ECF volume expansion, yet only a negligible amount of sodium appears in the final urine. This suggests that saline diuresis is the consequence of depressed distal sodium reabsorption. Previous clearance and micropuncture studies have not conclusively proven this.Eight dogs were studied repeatedly: in some studies glomerular filtration rate and distal delivery were increased markedly without sodium administration; in others comparably high distal sodium loads were achieved by progressive 1/2 isotonic saline infusion.CH:2o at high distal sodium loads was depressed by expansion of the ECF volume with hypotonic saline. The difference in free water formation between dogs which did and did not receive hypotonic saline was accounted for by the difference in sodium excretion. In one dog hypotonic saline expansion failed to depress free water formation; likewise the level of natriuresis in this dog was severely attenuated. The results of these experiments provide strong evidence that the natriuresis that occurs following ECF volume expansion with saline is a consequence of alteration in function of the distal nephron.

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Section: Methodssupporting

confidence: 91%

Effect of Extracellular Volume Expansion upon Sodium Reabsorption in the Distal Nephron of Dogs

Bennett¹

1973

J. Clin. Invest.

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“…During hypertonic saline loading, both normal and hypothyroid rats achieved very high osmolal clearance rates, greater than previously reported in this species (23,(26)(27)(28). As a result, it appears that fractional TCH2o in both groups reached a plateau when Cosm equaled approximately 24% of GFR, as no further increments could be detected even when fractional osmolal clearances were as high as 40-50 ml/min/100 ml GFR.…”

Section: Discussionmentioning

confidence: 57%

Mechanism of Impaired Water Excretion in the Hypothyroid Rat

Emmanouel¹,

Lindheimer²,

Katz³

1974

J. Clin. Invest.

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A B S T R A C r The ability to excrete an oral water load and the renal diluting mechanism were studied in hypothyroid rats and in age-matched euthyroid controls. Hypothyroid animals excreted a significantly smaller fraction of a 50-ml/kg oral water load than controls, demonstrating the same limited ability to excrete free water as thyroid-deficient man. During hypotonic (0.45%) saline infusion, absolute sodium delivery to the diluting segment and free water clearance were markedly lower in hypothyroid rats. However, both fractional distal sodium delivery and fractional free water clearance were similar in hypothyroid and control animals, suggesting that the reduced absolute free water formation in hypothyroid rats was due to decreased net distal delivery. In support of this hypothesis was the observation that fractional distal sodium reabsorption was equal or higher in thyroid-deficient rats, which indicates that the sodium reabsorptive capacity of the diluting segment was preserved in these animals. The results cannot be attributed to incomplete suppression of antidiuretic hormone (ADH) since they were identical in diabetes insipidus rats, nor to different rates of non-ADH-dependent backflux of filtrate since tissue osmolality and solute concentrations in the cortex, medulla, and papilla were similar in hypothyroid and control rats of both Sprague-Dawley and Brattleboro strains.The functional integrity of the diluting segment in hypothyroid rats was further demonstrated in experiments in which distal delivery was increased by contralateral nephrectomy or by administration of carbonic anhydrase inhibitors which decrease proximal sodium reabsorption. In both studies, fractional free water clearance increased markedly reaching levels significantly greater than in euthyroid controls. INTRODUCTIONHypothyroid man exhibits numerous renal functional defects, including decrements in glomerular filtration rate (GFR) , effective renal plasma flow (RPF), maximal urine osmolality, and free water generation and reabsorption (1, 2). In the rat, hypothyroidism is associated with similar reductions in GFR and RPF, along with a defect in tubular sodium reabsorption and a limited renal concentrating ability (3,4). Data on urinary dilution in the hypothyroid rat are not available.The most important clinical consequence of the renal functional defects in hypothyroid man is water retention and dilutional hyponatremia, due to the limited ability of the kidney to generate free water. The mechanism underlying this defect remains undefined, being variously attributed to inappropriate secretion of or increased tubular sensitivity to vasopressin (5-8), relative deficiency of adrenocortical hormones (9), defective distal sodium reabsorption (1), and decreased delivery of filtrate to the distal diluting segment (1, 2).The present study was designed to evaluate the renal diluting process in hypothyroid rats and to examine in this species some of the pathogenetic mechanisms ad1Abbreviations used in this paper: ADH, antidiuretic (Charles Ri...

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“…an association between prenatal exposure to betamethasone and GFR values, showing significantly higher GFR values (+O.11 + 0.03 mL/min) at d 3 after birth after ther in an increase in renal blood flow or in direct vaso-dilation of the renal vasculature (17,18). Baylis and Brenner (19) provided evidence in a carefully delineated micropuncture study that values for single-nephron GFR were 25% higher in rats treated with methylprednisolone.…”

Section: Resultsmentioning

confidence: 99%

Effects of Prenatal Exposure to Betamethasone and Indomethacin on the Glomerular Filtration Rate in the Preterm Infant

et al. 1994

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

Cited by 55 publications

References 18 publications

Effect of Extracellular Volume Expansion upon Sodium Reabsorption in the Distal Nephron of Dogs

Effect of Extracellular Volume Expansion upon Sodium Reabsorption in the Distal Nephron of Dogs

Mechanism of Impaired Water Excretion in the Hypothyroid Rat

Effects of Prenatal Exposure to Betamethasone and Indomethacin on the Glomerular Filtration Rate in the Preterm Infant

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