Renal concentrating operation in hypothermic dogs

1959 ◽  
Vol 196 (5) ◽  
pp. 1150-1154 ◽  
Author(s):  
Suk Ki Hong ◽  
John W. Boylan
Keyword(s):  
Steady State ◽  
Body Temperature ◽  
Isotonic Saline ◽  
Free Water ◽  
Tubular Reabsorption ◽  
Urine Flow ◽  
Constant Infusion ◽  
Threefold Increase ◽  
Anesthetized Dogs ◽  
Ice Water

The renal concentrating operation during hydropenia and during constant infusion of 2 m urea in isotonic saline was studied in 10 anesthetized dogs. PAH, exogenous creatinine and osmolal clearances were determined, as well as rates of Na and Cl excretion. Following two to four control periods body temperature was lowered to approximately 25°C by the use of an ice-water bath. The above measurements were then repeated during this steady state of hypothermia. PAH and creatinine clearances are reduced to approximately one-third of control values, while urine flow is not significantly changed. Thus, proportionately less filtered water is reabsorbed. Osmolal clearance is reduced, but this reduction is less than that of GFR so that a decrease in the tubular reabsorption of filtered osmotic particles occurs in hypothermia. This reduction in tubular reabsorption of solute is revealed further in a two to threefold increase in the percentage excretion of filtered NaCl and total osmotic substance. A greater decrease in the process which removes free water (TcHH2O) from the supposedly isotonic tubular fluid results in a reduction to one-third to one-fourth of the control values for TcHH2O. There would appear to be a dissociation of water and solute reabsorptions in hypothermia which indicates a decrease in the renal concentrating process.

Renal function, heart rate, and blood pressure during exercise and avoidance in dogs

1982 ◽  
Vol 242 (5) ◽  
pp. R482-R490
Author(s):  
A. Grignolo ◽  
J. P. Koepke ◽  
P. A. Obrist
Keyword(s):  
Heart Rate ◽  
Treadmill Exercise ◽  
Isotonic Saline ◽  
Free Water ◽  
Tubular Reabsorption ◽  
Urine Flow ◽  
Shock Avoidance ◽  
Free Water Clearance ◽  
Natriuretic Effect ◽  
Filtered Load

The effects of two behavioral tasks, treadmill exercise and shock avoidance, on renal and cardiovascular function were examined in dogs during intravenous infusion of isotonic saline. Urine was collected with a bladder catheter. Control experiments established steady base lines of urine flow (V), sodium excretion (UNaV), glomerular filtration rate (GFR), free water clearance (CH2O), heart rate (HR), and arterial pressure (Pa). Exercise led to increased V, UNaV, GFR, HR, and Pa with no change in CH2O. Avoidance caused decreases in V and UNaV, increases in HR and Pa but no change in either GFR or CH2O. The hematocrit increased significantly during both tasks. Exercise and avoidance led to opposite urinary changes even when HR accelerations were identical. The natriuretic effect of exercise was the consequence of an increased filtered load, while the antinatriuretic effect of shock avoidance was apparently due to an increased rate of tubular reabsorption of filtrate. The results show that exercise and shock avoidance, while eliciting similar cardiovascular changes, lead to opposite adjustments in urine and sodium output.

Relationship between turnover rate and blood concentration of lactate in exercising dogs

1975 ◽  
Vol 39 (2) ◽  
pp. 231-234 ◽  
Author(s):  
F. L. Eldridge
Keyword(s):  
Steady State ◽  
Blood Lactate ◽  
Turnover Rate ◽  
The Other ◽  
Constant Infusion ◽  
Blood Concentrations ◽  
Lactate Turnover ◽  
Anesthetized Dogs ◽  
Lactate Removal ◽  
The Relationship

Steady-state blood lactate concentrationss and lactate turnover, or entry, rates were determined by use of constant infusion of L(+)-[14C]lactate in seven anesthetized dogs before and during electrically induced exercise. Lactate entry rates increased during exercise in all dogs with or without the infusion of additional exogenous cold lactate. Blood lactate concentrations, on the other hand, rose to levels considerably below those predicted for these entry rates in a previous study of the relationship in normal nonexercising dogs. It is concluded that improved efficiency of lactate removal during exercise allows low blood concentrations despite large increases in entry rates.

Changes in glycerol kinetics after E. coli endotoxin administration in dogs

1984 ◽  
Vol 246 (3) ◽  
pp. R325-R330
Author(s):  
O. P. McGuinness ◽  
J. J. Spitzer
Keyword(s):  
Steady State ◽  
Infusion Rate ◽  
Volume Of Distribution ◽  
Constant Infusion ◽  
Metabolic Clearance ◽  
Glycerol Concentration ◽  
Endotoxin Administration ◽  
E Coli ◽  
The Face ◽  
Anesthetized Dogs

The metabolic clearance rate (MCR) and maximal rate of glycerol removal (Rd max) were determined in anesthetized dogs at two time periods after the intravenous administration of either Escherichia coli endotoxin or saline. The nonisotopic method employed in these studies to determine the MCR of glycerol consisted of a constant infusion of glycerol at three different infusion rates. At each infusion rate a steady-state glycerol concentration was obtained. The reciprocal of the slope of the linear relationship between the glycerol infusion rate and the change in the steady-state arterial glycerol concentration was equal to the MCR of glycerol. Administration of endotoxin significantly decreased the MCR of glycerol, whereas the volume of distribution of glycerol was not altered significantly. The arterial glycerol turnover remained unaltered, whereas arterial glycerol concentration increased after endotoxin administration. The studies demonstrate that the elevated arterial glycerol concentration maintained the rate of glycerol turnover in the face of decreased efficiency of glycerol removal after endotoxin administration.

Mannitol diuresis in hemorrhagic hypotension

1963 ◽  
Vol 204 (4) ◽  
pp. 555-562 ◽  
Author(s):  
G. Peters ◽  
H. Brunner
Keyword(s):  
Sodium Sulfate ◽  
Isotonic Saline ◽  
Urine Flow ◽  
Hemorrhagic Hypotension ◽  
Hypertonic Solutions ◽  
Anesthetized Dogs

In anesthetized dogs and cats bleeding to arterial pressures below 50 mm Hg did not cause anuria when infusions of hypertonic mannitol were given at 0.20–0.40 ml/kg·min. In animals infused with isotonic saline, urine flow stopped below 50 mm Hg, but could be re-established by infusion of hypertonic solutions of mannitol, sodium sulfate, or urea. In both groups urine flow finally stabilized at 5–40%, and GFR (CIn) at 2–14% of prehemorrhagic values. CCr(exog)/CIn fell to values below unity in hemorrhagic hypotension in most dogs. In most cats CCr(exog) /CIn was larger than 1.10, and was lowered in hemorrhagic hypotension.

Renal activity of vasopressin in anesthetized dogs

1961 ◽  
Vol 200 (2) ◽  
pp. 400-404 ◽  
Author(s):  
Joseph H. Perlmutt
Keyword(s):  
Filtration Rate ◽  
Renal Plasma Flow ◽  
Free Water ◽  
Urine Osmolality ◽  
Urine Flow ◽  
Urinary Concentration ◽  
Urinary Ph ◽  
Free Water Clearance ◽  
Anesthetized Dogs ◽  
Sustained Increase

Conventional clearance techniques were used to study the renal response to vasopressin (5–100 mu/hr.) infused for 2 1/2 hours into anesthetized (pentobarbital), surgically traumatized dogs elaborating a dilute urine. Decreased urine flow, a concomitant sustained increase in Na+ excretion, increased urine osmolality, negative free-water clearance and an increased osmolal U/P ratio (>1, <2) consistently occurred during the infusion of 50 mu/hr. Urinary pH rose and HCO3–, rather than Cl–, was the predominant anion excreted. Tubular rejection of HCO3–, however, is not essential for vasopressin activity under the conditions of this investigation since antidiuresis occurred in an acidotic dog. Usually some increase in glomerular filtration rate and effective renal plasma flow were apparent during vasopressin infusion; the former change could account for the increased Na+ excretion, but it is difficult to ascribe the peculiar anion behavior to this factor. Maximum urinary concentration was not attained even with 100 mu vasopressin/hr.

Tubular handling of fluid and electrolytes during ovine pregnancy

1993 ◽  
Vol 265 (2) ◽  
pp. F278-F284 ◽  
Author(s):  
S. C. Cha ◽  
G. W. Aberdeen ◽  
S. Mukaddam-Daher ◽  
E. W. Quillen ◽  
B. S. Nuwayhid
Keyword(s):  
Isotonic Saline ◽  
Free Water ◽  
Tubular Reabsorption ◽  
Distal Nephron ◽  
Free Water Clearance ◽  
Sodium Accumulation ◽  
Saline Loading ◽  
Pregnant Sheep ◽  
Proximal Tubular ◽  
Proximal Tubular Reabsorption

Pregnancy is characterized by progressive water and sodium accumulation and increases in renal blood flow (RBF) and glomerular filtration rate (GFR). However, the influence of the different nephron segments on the increased tubular reabsorption is controversial. Consequently, four nonpregnant and five pregnant sheep were studied, after chronic instrumentation, to assess salt and water reabsorption in the proximal and distal tubules under basal and volume-loaded conditions. Lithium clearance was used as a marker for proximal tubular reabsorption. Volume loading was achieved by the rapid administration of 1,000 ml isotonic saline followed by 250 ml/h for 2 h. Under basal conditions with reference to the nonpregnant state, pregnant sheep had higher (P < 0.05) levels of right RBF (427 +/- 34 vs. 313 +/- 8 ml/min), GFR (133 +/- 7 vs. 94 +/- 9 ml/min), proximal tubular reabsorption (102 +/- 7 vs. 73 +/- 6 ml/min), distal nephron fluid delivery (31 +/- 2 vs. 20 +/- 2 ml/min), and fractional distal nephron reabsorption of fluid (92 +/- 2 vs. 87 +/- 1%) and sodium (98.8 +/- 0.3 vs. 97.0 +/- 0.7%). However, pregnant animals had significantly (P < 0.05) reduced fractional excretions of fluid (1.6 +/- 0.3 vs. 2.6 +/- 0.2%) and sodium (0.24 +/- 0.06 vs. 0.63 +/- 0.19%), but similar levels of filtration fraction, fractional proximal tubular reabsorption, urine flow, urinary sodium excretion, and osmolar and free water clearance. After saline loading, pregnant sheep excreted significantly (P < 0.05) less sodium (9.2 vs. 28.6%) and water (39.8 vs. 56.5%). Decreases in fractional proximal and distal nephron reabsorption of sodium and water after saline loading were attenuated in pregnant animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal tubular reabsorptive response to hypernatremia

1976 ◽  
Vol 231 (2) ◽  
pp. 642-649 ◽  
Author(s):  
EH Bresler ◽  
KT Nielsen ◽  
Miller MC ◽  
MR Stoud
Keyword(s):  
Isotonic Saline ◽  
Sodium Concentration ◽  
Tubular Reabsorption ◽  
Plasma Sodium ◽  
Plasma Protein Concentration ◽  
Bulk Fluid ◽  
Plasma Sodium Concentration ◽  
Anesthetized Dogs ◽  
Total Body ◽  
Renal Tubular

Renal tubular reabsorptive response to rapid infusions of isotonic saline and 5% NaCl solutions were measured during brisk ethacrynic acid diuresis in anesthetized dogs. When adjustments were made for effects of variations in volume expansion, as indexed by plasma protein concentration ([Pprot]), tubular reabsorption of sodium per unit filtrate volume (TNa/GFR) was found to be significantly and positively correlated with plasma sodium concentration ([PNa]) despite hypernatremia and total body surfeit of sodium. The proportions of sodium and water reabsorbed were also homeostatically inappropriate, since the sodium concentration in the reabsorbate was somewhat in excess of that in contemporary plasma ultrafiltrate. These findings signify that glomerulotubular balance holds when the filtered load of sodium is increased by an increment in [pNa] as well as GFR. It is proposed that the moiety of tubular reabsorption (some 75% of GFR) studied here is more closely related to regulation of volume than of osmolality of sodium concentration, and the primary regulation exerted is on tubular volume reabsorption (bulk fluid reabsorption) rather than on the amount of sodium reabsorbed.

Influence of hydration on renal function and medullary sodium during vasopressin infusion

1962 ◽  
Vol 202 (6) ◽  
pp. 1098-1104 ◽  
Author(s):  
Joseph H. Perlmutt
Keyword(s):  
Renal Function ◽  
Glomerular Filtration Rate ◽  
Filtration Rate ◽  
Urine Flow ◽  
Constant Infusion ◽  
Water Diuresis ◽  
Vasopressin Infusion ◽  
Degree Of Hydration ◽  
Anesthetized Dogs ◽  
Influence Of Hydration

Mild and severe degrees of hydration were produced in anesthetized dogs by constant infusion of dextrose in water at different rates. When water diuresis ensued, and after adequate control periods, vasopressin was infused for 2 1/2 hr. The magnitudes of urine flow and Na excretion varied directly and osmolal urine-to-plasma ratio varied inversely with the degree of hydration. During mild hydration, glomerular filtration rate and osmolal clearance remained practically unchanged, whereas during severe hydration they increased. In another group of animals, similarly prepared, kidneys were removed at appropriate times and tissue was obtained from various areas for Na analysis. During uninterrupted water diuresis the medullary gradient for Na was practically dissipated. Vasopressin promoted the repletion of medullary Na during mild hydration, but only slightly ameliorated the disturbance during severe hydration. These data demonstrate that during vasopressin infusion the renal concentrating response and Na excretion were significantly modified by the degree of hydration, and evidence is presented for several possible causes.

Reflex antidiuresis after occlusion of common carotid arteries in hydrated dogs

1963 ◽  
Vol 204 (2) ◽  
pp. 197-201 ◽  
Author(s):  
Joseph H. Perlmutt
Keyword(s):  
Antidiuretic Hormone ◽  
Time Course ◽  
Carotid Arteries ◽  
Free Water ◽  
Urine Flow ◽  
Free Water Clearance ◽  
Renal Vasoconstriction ◽  
Anesthetized Dogs ◽  
The Common ◽  
Common Carotid Arteries

Common carotid arteries were occluded bilaterally for 5 min below the thyrocarotid arterial junctions in mildly hydrated, anesthetized dogs. Within 5–15 min after the occlusion, urine flow declined and remained below control values for 30–105 min. Concurrently, the urine became hypertonic to systemic plasma and there was no evidence for renal vasoconstriction or increased solute reabsorption. The decrement in urine flow was accounted for entirely by the decline in free-water clearance. Prolonged periods of occlusion or increased hydration altered the response. Bilateral occlusion of the common carotid arteries for 5 min above intact thyrocarotid arterial junctions (but below the carotid sinuses) or below denervated thyrocarotid arterial junctions did not affect urine flow. The time course of the response, the characteristics of the urine, and the absence of renal vasoconstriction suggest that the procedure induced a reflex release of antidiuretic hormone. Furthermore, the data indicate that the receptor area for this reflex is located in the region of the junction of the common carotid and thyroid arteries.

Effect of Body Temperature on Pulmonary Gas Exchange

1957 ◽  
Vol 188 (2) ◽  
pp. 355-359 ◽  
Author(s):  
A. B. Otis ◽  
James Jude
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Steady State ◽  
Body Temperature ◽  
Gas Exchange ◽  
Diffusing Capacity ◽  
Body Temperatures ◽  
Pulmonary Diffusing Capacity ◽  
Normal Body ◽  
Anesthetized Dogs

Measurements were made of the arterial-alveolar carbon dioxide gradient in anesthetized dogs at body temperatures ranging from normal down to 16°C. Pulmonary diffusing capacity was determined by a steady-state carbon monoxide method in anesthetized dogs at normal body temperatures and at 25°C. From the results it is concluded that although diffusing capacity is reduced at low body temperatures, it is still adequate for transfer of both CO2 and O2 because the metabolic requirements for gas exchange are also reduced.

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