The Freezing Point Depression of Mammalian Tissues After Sudden Heating in Boiling Distilled Water

A B S T R A C T The effects of acute unilateral ureteral obstruction (UUO) of 18 h duration on deep nephron function was evaluated in 14 weanling rats with the technique of micropuncture. After release of UUO, 3.40+0.66% (SE) of the filtered water remained at the tip of the collecting duct nearly fivefold greater than in controls (0.75±0.10%). Similar differences were seen in fractional sodium that remained at this site. The ratio of tubular fluid osmolality to that of plasma was also reduced in the UUO group (1.53±0.06 vs. 4.60±0.26 in controls, P < 0.001).Single nephron glomerular filtration rate of cortical and deep nephrons was significantly less (P < 0.001) after release of UUO. Although the percentage of filtering nephrons was significantly reduced in both nephron populations, the decline in glomerular filtration rate was greater in cortical than in juxtamedullary nephrons (cortical:juxtamedullary nephrons = 27.6+4.5% vs. 53.3±5.2% in controls, P < 0.005) which suggests that single nephron glomerular filtration rate is redistributed to deep nephrons after release of UUO. In contrast to cortical nephrons, the amount oftubular fluid which remains near the bend of the loop of Henle of deep nephrons was greater after release of UUO. This appeared to be the result of a decrease in the reabsorption of both water (tubular fluid:plasma inulin = 2.41+0.16 vs. 7.94±0.69 in controls, P < 0.001) and sodium (52.3±4% vs. 40.7±2.9% of the filtered sodium in controls, P < 0.02). It is suggested that this altered in controls, P < 0.001) which indicates that the decline in papillary osmolality is not a consequence of the increased IMPF seen after ureteral release, but rather precedes it. In fact, the decline in papillary osmolality may contribute to the increase in IMPF after release of UUO and to the decreased reabsorption offluid along the descending limb of the loop of Henle.

Section: Methodsmentioning

confidence: 99%

Deep nephron function after release of acute unilateral ureteral obstruction in the young rat.

Buerkert¹,

Martin²,

Head³

et al. 1978

“…'2-Benzenesulfonamido-1,3,4-thiadiazole-5-sulfonamide supplied through the courtesy of Dr. Robert T. Kunau, Jr. processed according to a modification of the method of Appelboom, Brodsky, Tuttle, and Diamond (13). The capsules were stripped and the kidneys cut along the longitudinal axis.…”

Section: Methodsmentioning

confidence: 99%

Mechanism of Impaired Water Excretion in the Hypothyroid Rat

Emmanouel¹,

Lindheimer²,

Katz³

1974

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...

“…in normal (n = 7), saltdepleted (n = 6), and aldosterone-loaded normal dogs (n = 3) during hypotonic saline infusion. o Normal Dogs (7) * ANesteros" Leadod Dlgs (3) * Sall Depleted legs (6) *-.. UNaY fleq/min FIGURE 3 Comparison of the relationship between potassium excretion (UKV) and sodium excretion (UNaV) in normal dogs, aldosterone-loaded dogs, and salt-depleted dogs during hypotonic saline infusion.…”

Section: Resultsmentioning

confidence: 99%

“…Papillary tip osmolality was determined by the method of Appelboom et al (6). The only modification was that the tissue-was partially frozen (as described above) for ease of handling.…”

Section: Introductionmentioning

confidence: 99%

Evidence for enhanced distal tubule sodium reabsorption in chronic salt-depleted dogs.

Chou¹,

Ferder²,

Levin³

et al. 1976

AB STRA CT In order to assess the renal tubular site(s) at which sodium reabsorption is enhanced in chronic sodium-depletion, seven normal dogs, six saltdepleted dogs, and three normal dogs receiving aldosterone were studied during a steady-state water diuresis under Pentothal anesthesia and during progressive hypotonic saline diuresis. For both maintenance of the water diuresis and progressive hypotonic saline diuresis 0.45% NaCl was used. During the steady state water diuresis delivery of sodium to the diluting segment of the nephron as approximated by solute-free water clearance + sodium clearance/glomerular filtration rate (CH2O + CN./GFR) was significantly lower in salt-depleted dogs compared to normal dogs with or without aldosterone. During progressive hypotonic saline infusion fractional free water excretion (CH20/GFR) was similar in all three groups as CHn>O + CNa/GFR increased up to 12-14 ml /min. 100 ml GFR. Thereafter, CH20/ GFR continued to rise in virtually a straight line in salt-depleted dogs but leveled off in normal dogs with or without aldosterone. These data demonstrate that enhanced sodium reabsorption in the diluting segment of the nephron is an important determinant of the renal sodium retention in chronic extracellular volume contraction in dogs in addition to confirming the presence of increased proximal tubule sodium reabsorption in these animals.