EFFECT OF HYPOTHALAMIC LESIONS ON WATER METABOLISM OF THE TOAD BUFO MARINUS

1977 ◽  
Vol 75 (1) ◽  
pp. 161-172 ◽  
Author(s):  
H. R. BAKKER ◽  
S. D. BRADSHAW
Keyword(s):  
Water Uptake ◽  
Functional Significance ◽  
Free Water ◽  
Fluid Retention ◽  
Water Metabolism ◽  
Free Water Clearance ◽  
Hypothalamic Lesions ◽  
Antidiuretic Effect ◽  
Saturated Atmosphere ◽  
Toad Bufo

The rate of cutaneous water uptake after dehydration was significantly depressed in functionally neurohypophysectomized toads (Bufo marinas), which consequently regained weight much more slowly than intact toads when returned to water. Toads bearing hypothalamic lesions were able to develop an antidiuresis when removed from water to a saturated atmosphere, but the antidiuresis was solely glomerular in origin and was established more slowly than in intact animals. The fractional reabsorption of filtrate increased significantly and the relative free water clearance decreased significantly in intact toads after removal from water. These changes in tubular function, which were not seen in lesioned toads, were responsible for the development of a more rapid and effective antidiuresis in intact animals. Injections of iso-osmotic saline, oxytocin (250 mu./100 g) and vasopressin (50 mu./100 g) had no significant effect on rates of cutaneous water uptake in both intact and lesioned toads. Injections of hyperosmotic saline, however, significantly increased rates of water uptake in both groups of toads, but to a much greater extent in the intact animals. Fluid retention arising from a marked antidiuresis occurred after the injection of vasopressin and hyperosmotic saline, and there was some evidence of an antidiuretic effect of oxytocin with the doses used here. These results and their bearing on the question of the functional significance of the neurohypophysis in anuran amphibians are discussed.

scholarly journals Application of the clearance concept to hyponatremic and hypernatremic disorders: a phenomenological analysis

1994 ◽  
Vol 40 (7) ◽  
pp. 1220-1227 ◽  
Author(s):  
A S Shoker
Keyword(s):  
Free Water ◽  
Phenomenological Analysis ◽  
Water Metabolism ◽  
Protective Mechanisms ◽  
Free Water Clearance ◽  
Water Homeostasis ◽  
Clinical Method ◽  
Clearance Concept ◽  
Water Clearance

Abstract The kidney and its response to the antidiuretic hormone (ADH) are the principal protective mechanisms necessary to maintain a normal plasma tonicity (osmolality). Hence, determination of the response of the ADH-renal axis to an abnormal plasma tonicity is an important step to understanding water homeostasis. Determination of free water clearance is the most direct clinical method to measure the ability of the kidney to reabsorb or excrete water; it can be used as a sensitive method to study water metabolism, describing the abnormal water homeostasis in simple quantitative terms. A positive electrolyte-free water clearance denotes the excretion of excess free water. A negative electrolyte-free water clearance indicates reabsorption of excess free water. During hypertonicity, an increased concentration of ADH enhances renal reabsorption of free water. With diminished ADH secretion and normal renal function, a substantial volume of free water is cleared in response to hypotonic stimuli. A positive free water clearance > 0.4 L/day in hypertonic conditions or a negative free water clearance during hypotonicity confirms an abnormal ADH-renal axis response.

Early fluid retention and severe acute mountain sickness

2005 ◽  
Vol 98 (2) ◽  
pp. 591-597 ◽  
Author(s):  
Jack A. Loeppky ◽  
Milton V. Icenogle ◽  
Damon Maes ◽  
Katrina Riboni ◽  
Helmut Hinghofer-Szalkay ◽  
...  
Keyword(s):  
Acute Mountain Sickness ◽  
Plasma Concentrations ◽  
Free Water ◽  
Plasma Renin ◽  
Barometric Pressure ◽  
Respiratory Alkalosis ◽  
Fluid Retention ◽  
Free Water Clearance ◽  
Water Excretion ◽  
Mountain Sickness

Field studies of acute mountain sickness (AMS) usually include variations in exercise, diet, and environmental conditions over days and development of clinically apparent edemas. The purpose of this study was to clarify fluid status in persons developing AMS vs. those remaining without symptoms during simulated altitude with controlled fluid intake, diet, temperature, and without exercise. Ninety-nine exposures of 51 men and women to reduced barometric pressure (426 mmHg = 16,000 ft. = 4,880 m) were carried out for 8–12 h. AMS was evaluated by Lake Louise (LL) and AMS-C scores near the end of exposure. Serial measurements included fluid balance, electrolyte excretions, and plasma concentrations, regulating hormones, and free water clearance. Comparison between 16 subjects with the lowest AMS scores near the end of exposure (“non-AMS”: mean LL = 1.0, range = 0–2.5) and 16 others with the highest AMS scores (“AMS”: mean LL = 7.4, range = 5–11) demonstrated significant fluid retention in AMS beginning within the first 3 h, resulting from reduced urine flow. Plasma Na+ decreased significantly after 6 h, indicating dilution throughout the total body water. Excretion of Na+ and K+ trended downward with time in both groups, being lower in AMS after 6 h, and the urine Na+-to-K+ ratio was significantly higher for AMS after 6 h. Renal compensation for respiratory alkalosis, plasma renin activity, aldosterone, and atrial natriuretic peptide were not different between groups, with the latter tending to rise and aldosterone falling with time of exposure. Antidiuretic hormone fell in non-AMS and rose in AMS within 90 min of exposure and continued to rise in AMS, closely associated with severity of symptoms and fluid retention.

Aldosterone effects on water and electrolyte metabolism

1984 ◽  
Vol 100 (1) ◽  
pp. 93-100 ◽  
Author(s):  
C. J. Kenyon ◽  
N. A. Saccoccio ◽  
D. J. Morris
Keyword(s):  
Body Weight ◽  
Water Balance ◽  
Urine Volume ◽  
Free Water ◽  
The Body ◽  
Sodium Balance ◽  
Plasma Sodium ◽  
Transient Effects ◽  
Water Metabolism ◽  
Free Water Clearance

ABSTRACT The effects of constant infusions of small doses of adrenal steroid hormones on sodium, potassium and water metabolism were studied in male adrenalectomized rats. An infusion of 1 μg aldosterone/day was sufficient to restore normal sodium and potassium balance in a group of rats fed an unsupplemented diet. Log doses of aldosterone (0·1–10 μg/day for 4 days) administered some days after adrenalectomy caused linear increases in the body weight of rats fed a sodium-supplemented diet (0·05 m-NaCl as drinking fluid) during 4 days of treatment. Increases in body weight correlated with renal sodium and water balance. When steroid treatment was started at the time of adrenalectomy, sodium balance was not significantly affected although rats treated with 1 μg aldosterone/day ate more, drank less saline, produced a smaller volume of urine of greater osmolarity and gained more weight than controls. A dose of 100 μg 18-hydroxy-deoxycorticosterone/day had no significant effects. Fluid intake and urine volume were not significantly affected by 1 mg corticosterone/day but food intake, water balance and weight gain were greater than controls. Rats treated with both aldosterone and corticosterone showed a decrease in free water clearance. Aldosterone and corticosterone, both singly and in combination, reduced plasma potassium levels. Plasma sodium levels were only increased when aldosterone was administered on its own. Long-term steroid infusions have revealed more about the physiology of aldosterone action than could acute measurements of renal function. In particular, they have indicated that dietary intake of electrolytes as well as excretion are affected, that mineralocorticoid actions are distinct from glucocorticoid actions and that there are transient effects of aldosterone on fluid regulation which are not sustained under steady-state conditions. J. Endocr. (1984) 100,93–100

Cooperative mechanisms of acute antidiuretic response to bendroflumethiazide in rats with lithium-induced nephrogenic diabetes insipidus

2010 ◽  
Vol 88 (12) ◽  
pp. 1191-1201 ◽  
Author(s):  
S. Mostafa Shid Moosavi ◽  
Masoud Haghani
Keyword(s):  
Diabetes Insipidus ◽  
Nephrogenic Diabetes Insipidus ◽  
Urine Volume ◽  
Free Water ◽  
Urine Flow ◽  
Water Reabsorption ◽  
Free Water Clearance ◽  
Urinary Osmolality ◽  
Antidiuretic Effect ◽  
Water Clearance

The exact mechanism underlying thiazides-induced paradoxical antidiuresis in diabetes insipidus is still elusive, but it has been hypothesized that it is exerted either via Na+-depletion activating volume-homeostatic reflexes to decrease distal delivery, or direct stimulation of distal water reabsorption. This study examined how these two proposed mechanisms actually cooperate to induce an acute bendroflumethiazide (BFTZ)-antidiuretic effect in nephrogenic diabetes insipidus (NDI). Anaesthetized rats with lithium (Li)-induced NDI were prepared in order to measure their renal functional parameters, and in some of them, bilateral renal denervation (DNX) was induced. After a 30 min control clearance period, we infused either BFTZ into 2 groups, NDI+BFTZ and NDI/DNX+BFTZ, or its vehicle into a NDI+V group, and six 30 min experimental clearance periods were taken. During BFTZ infusion in the NDI+BFTZ group, transiently elevated Na+ excretion was associated with rapidly increased urinary osmolality and decreased free water clearance, but Li clearance and urine flow declined in the later periods. However, in the NDI/DNX+BFTZ group, there was persistently elevated Na+ excretion with unchanged Li clearance and urine flow during the experimental period, while alterations in free water clearance and urinary osmolality resembled those in the NDI+BFTZ group. In conclusion, BFTZ initially exerted two direct effects of natriuresis–diuresis and stimulating free water reabsorption at the distal nephron in NDI, which together elevated Na+ excretion and urinary osmolality but kept the urine volume unchanged in the first hour. Thereafter, the resultant sodium depletion led to the activation of neural reflexes that reduced distal fluid delivery to compensate for BFTZ-induced natriuresis–diuresis which, in cooperation with the direct distal BFTZ-antidiuretic effect, resulted in excretion of urine with a low volume, high osmolality, and normal sodium.

The effect of indomethacin on the renal response to arginine vasopressin in man

1986 ◽  
Vol 70 (5) ◽  
pp. 409-416 ◽  
Author(s):  
J. J. Dixey ◽  
T. D. M. Williams ◽  
S. L. Lightman ◽  
A. F. Lant ◽  
D. A. Brewerton
Keyword(s):  
Arginine Vasopressin ◽  
Excretion Rate ◽  
Plasma Concentrations ◽  
Free Water ◽  
Significant Inhibition ◽  
Free Water Clearance ◽  
Renal Response ◽  
Physiological Range ◽  
Antidiuretic Effect ◽  
Sodium Clearance

1. The renal response to graded intravenous infusions of arginine vasopressin (AVP) was investigated in a two part study in six volunteers. First, under maximal water diuresis, seven control incremental infusions of AVP were given from zero to 12 fmol min−1 kg−1. Second, the AVP infusions were repeated after pretreatment with indomethacin, 150 mg daily for 36 h. 2. After the AVP infusions, plasma AVP concentrations did not change significantly and remained within the physiological range; in contrast, urinary AVP excretion rate increased steadily. Indomethacin did not alter the plasma or urinary concentrations of AVP. 3. AVP caused a fall in urine flow rate from a state of maximal diuresis to one of maximal anti-diuresis. After indomethacin, fractional free water clearance was reduced by an average of 26% at the zero, 2 and 4 fmol min−1 kg−1 infusion rates of AVP. 4. A significant increase in fractional sodium clearance of approximately 50% occurred during the AVP infusions, which was abolished after pretreatment with indomethacin. 5. After indomethacin, urinary prostaglandin E2 (PGE2) excretion rate was reduced by an average of 40%) at the zero and 2 fmol min−1 kg−1 infusion rates of AVP. At higher AVP infusion rates, no significant inhibition of PGE2 was observed. 6. Urinary kallikrein excretion rate decreased steadily to one-third of its original value after AVP and this change remained unaltered by indomethacin. 7. The findings show that infusions of AVP, resulting in plasma concentrations in the physiological range, evoke a maximal antidiuretic response, which is accompanied by natriuresis. Significant inhibition of urinary prostaglandin excretion by indomethacin is accompanied by both enhancement of the antidiuretic effect of an abolition of the natriuretic response to AVP.

Increased Renal Reabsorption of Osmotically Free Water by the Toad (Bufo marinus) in Response to Neurohypophysial Hormones

1957 ◽  
Vol 189 (3) ◽  
pp. 564-568 ◽  
Author(s):  
Wilbur H. Sawyer
Keyword(s):  
Free Water ◽  
Bufo Marinus ◽  
Common Mechanism ◽  
Water Reabsorption ◽  
Free Water Clearance ◽  
Water Excretion ◽  
Neurohypophysial Hormones ◽  
Consistent Feature ◽  
Toad Bufo ◽  
Antidiuretic Action

Neurohypophysial extracts or dehydration produce a pronounced antidiuresis in Bufo marinus. The antidiuretic mechanism was studied by following creatinine, inulin and free-water clearances in unanesthetized toads. Urine was collected directly from the ureters to avoid errors due to water reabsorption through the bladder. A decrease in free-water clearance is a consistent feature and accounts for most of the antidiuresis. There may also be a decrease in filtration rate. The effect of neurohypophysial hormones on free water excretion is attributed to an increase in the permeability of the tubule to the osmotic inflow of water. The similarity between the action of neurohypophysial hormones on the skin, the bladder and the renal tubule of Amphibia suggests a common mechanism, namely the dilatation of pores. The hypothesis is also advanced that the antidiuretic action of neurohypophysial hormones on the mammalian kidney depends on the same mechanism.

scholarly journals Water metabolism disturbances at different stages of primary thyroid failure

2001 ◽  
Vol 168 (3) ◽  
pp. 435-445 ◽  
Author(s):  
M Sahun ◽  
C Villabona ◽  
P Rosel ◽  
MA Navarro ◽  
JM Ramon ◽  
...  
Keyword(s):  
Plasma Osmolality ◽  
Free Water ◽  
Plasma Renin ◽  
Primary Hypothyroidism ◽  
Plasma Aldosterone ◽  
Water Metabolism ◽  
Loading Test ◽  
Free Water Clearance ◽  
Natriuretic Hormone ◽  
Replacement Treatment

The aim of the present study was to study salt and water metabolism in thyroid deficiency. We performed an oral water loading test (OWL) and a hypertonic 5% saline infusion test (HSI) in 16 patients with overt primary hypothyroidism before replacement treatment (PRE group) and after, in eight patients with subclinical hypothyroidism (SUB group) and in 16 normal individuals (CG group). In the PRE group, a lower free water clearance was detected in the OWL (P < 0.022), with lower plasma osmolality (OWL: P < 0.005; HSI: P < 0.001) and arginine vasopressin (AVP) (OWL: P < 0.001; HSI: P < 0.001) than the CG group, across both tests; they normalized with the replacement treatment. The same plasma abnormalities were detected in the SUB group with the HSI. Although the AVP and thirst thresholds did not differ between the groups, the lag between them was lower in the PRE (4.1+/-3.2 mOsm/kg) and SUB group (2.6+/-2.1 mOsm/kg) than in the CG group (13.3+/-9.2 mOsm/kg) (P < 0.05). There were no differences in atrial natriuretic hormone (ANH), plasma renin activity (PRA) and plasma aldosterone among the groups. These results indicate that plasma hypo-osmolality and low levels of AVP are present in primary hypothyroidism, and indeed are already present in the subclinical phase of the disease. An overlap between the thresholds of thirst and AVP seem to play a role in these abnormalities, but ANH, PRA and plasma aldosterone do not appear to contribute.

Glycerol hyperhydration: hormonal, renal, and vascular fluid responses

1995 ◽  
Vol 79 (6) ◽  
pp. 2069-2077 ◽  
Author(s):  
B. J. Freund ◽  
S. J. Montain ◽  
A. J. Young ◽  
M. N. Sawka ◽  
J. P. DeLuca ◽  
...  
Keyword(s):  
Atrial Natriuretic Peptide ◽  
Free Water ◽  
Fluid Retention ◽  
Urine Flow ◽  
Plasma Aldosterone ◽  
Water Reabsorption ◽  
Free Water Clearance ◽  
Flow Rates ◽  
Total Body ◽  
Water Clearance

Glycerol ingestion has been shown to mediate hyperhydration; however, the mechanism(s) responsible for this improved fluid retention is not well understood. This study examined the hormonal, renal, and vascular fluid responses to glycerol hyperhydration in 11 resting male volunteers who ingested one of two experimental solutions and then a water bolus. The volume of fluid ingested was determined from the subjects' measured total body water (TBW; total volume = 37 ml/l TBW, 1,765 +/- 162 ml). Experimental solutions (5.0 ml/l TBW) were matched for color and taste and differed only in that one contained 1.5 g glycerol/l TBW (total osmolar load = 777 +/- 24 mosmol). Nine of the 11 subjects also completed a control trial during which no fluid was ingested. Glycerol ingestion (GI) resulted in greater fluid retention than the ingestion of water alone (WI; 60 vs. 32% 3-h posthyperhydration, P < 0.01). This improved fluid retention with GI resulted from lower urine flow rates (peak 6.2 vs. 10.5 ml/min, P < 0.01) associated with lower free water clearance rates (peak = 1.2 vs. 8.2 ml/min, P < 0.01). Hyperhydration had no effect on plasma atrial natriuretic peptide concentrations. Changes in plasma aldosterone were unrelated to differences in fluid retention. Antidiuretic hormone concentrations (ADH) were significantly reduced from prehyperhydration levels during both hyperhydration trials but tended (P = 0.07) to rise during GI compared with WI at the very time urine flow and free water clearance differences were also evident. This suggests that ADH may, in part, be responsible for glycerol's effectiveness, although differences in ADH concentrations were small and near the assay's sensitivity limits. Alternatively, glycerol's effectiveness may result from its directly increasing the kidneys' medullary concentration gradient and, hence, water reabsorption.

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