Gestation‐dependent Aspects of the Response of the Ovine Fetus to the Osmotic Stress Induced by Maternal Water Deprivation

Bell, R. J.; Congiu, M; Hardy, Kenneth J.; Wintour, E. M.

doi:10.1113/expphysiol.1984.sp002779

Cited by 32 publications

(13 citation statements)

References 15 publications

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“…Maternal water restriction significantly alters maternal and fetal fluid dynamics (3)(4)(5)(6). In the pregnant ewe, dehydrationinduced maternal plasma hyperosmolality and hypernatremia are associated with elevated levels of plasma AVP.…”

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confidence: 99%

“…Fetal plasma osmolality and sodium concentrations parallel maternal values, whereas increases in fetal plasma AVP are gestation-dependent (3). The fetus also may exhibit a relative decrease in plasma volume, glomerular filtration rate, and urine production (3)(4)(5). Urinary hyperosmolality, mediated in part by increased plasma AVP, contributes to increased amniotic fluid osmolality (1-3), whereas reduced urine production likely contributes to decreased amniotic fluid volume during dehydration (6).…”

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confidence: 99%

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Fetal Rehydration Via Intraamniotic Fluid: Contribution of Fetal Swallowing

et al. 1991

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ABSTRACT. Amniotic fluid volume is regulated by a balance of fetal fluid production and resorption. Although fetal swallowing is believed to be a major site of fluid resorption, additional routes of fluid exchange also may contribute. In our present study, five chronically prepared, water-restricted, pregnant ewes with singleton fetuses (128 f 1 d) were rehydrated via an intraamniotic infusion (100 mL/h over 90 min) of 0.075 M saline. In response to the maternal water restriction, significant increases were noted in maternal and fetal plasma osmolalities (306

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confidence: 99%

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Fetal Rehydration Via Intraamniotic Fluid: Contribution of Fetal Swallowing

et al. 1991

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“…We have suggested previously that the renal function of the premature or growth-retarded neonate might resemble that of the fetus rather than that of the normal newborn, and shown that cortisol has a unique natriuretic effect in the immature ovine fetal kidney (5). The immature fetal kidney is less responsive to endogenous or exogenous AVP than is the kidney of the nearterm fetus (6,7). With the discovery of an endogenous natriuretic peptide of atrial origin (8,9) it seemed to be important to find out whether this peptide exerted any influence over sodium handling by the immature fetal kidney.…”

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confidence: 99%

Action of Atrial Natriuretic Peptide in the Immature Ovine Kidney

et al. 1987

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ABSTRACT. This study examines the effects of infused human atrial natriuretic peptide 1-28 (hANP) on ovine fetal renal function. hANP was infused into chronically cannulated ovine fetuses of 103-128 days gestation (term 142-152 days) at 1.1 (4), 2.2 (5), and 4.4 (5) ~g / h for 2 h. Isotonic saline was infused in 10 control experiments. The fractional reabsorption of infused lithium was used as a marker of proximal tubular sodium reabsorption. Glomerular filtration rate and urinary water and electrolyte excretion were assessed. The blood pressure and heart rate were unaltered by any dose of hANP. The lowest dose (1.1 pg/h) did not produce any significant changes in glomerular filtration rate, urinary electrolyte or water excretion, or fractional reabsorption of lithium. hANP, at 4.4 pg/h, caused a significant ( p < 0.001) 5-fold increase in the excretion of Na, Cl, and Ca, doubled the excretion rate of K and free water clearance, and significantly increased glomerular filtration rate. Fractional sodium reabsorption and fractional reabsorption of lithium were significantly decreased ( p < 0.001, < 0.01, respectively). The results show that the fetal kidney, at this stage, is as responsive to hANP as is the adult kidney. The natriuretic action of hANP is related to increases in glomerular filtration rate and proximal tubular rejection of sodium (as assessed by fractional reabsorption of lithium). The excessive salt loss of the premature or low birth weight neonate, which also involves increased delivery of filtrate to the distal tubule, may be due to endogenous hANP, circulating at high concentrations. (Pediatr Res 22: 11-15, 1987) Abbreviations hANP, human atrial natriuretic peptide 1-28 GFR, glomerular filtration rate FRN,, fractional reabsorption of sodium FRj,j, fractional reabsorption of lithium UN., K , c,, ca V, renal excretion rate of sodium/potassium/ chloride/calcium CIIzo, free water clearance AVP, arginine vasopressin C,.i, clearance of lithium MAP, mean arterial pressure HR, heart rate

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“…The association between a relative expansion of blood volume (rate of increase above the 95o% confidence limit of the slope of controls) during maternal dehydration and the presence of hypertonic urine in the fetus suggests that ADH may be involved in this mechanism. The relative expansion of fetal blood volume during maternal dehydration occurred in fetuses close to term and our previous study (Bell et al 1984) showed that a mature fetus has a greater capacity to mobilize ADH in response to an osmotic stimulus than an immature fetus. This study thus suggests that ADH release by the ovine fetus during maternal water deprivation is in response to an osmotic stimulus and not fetal hypovolaemia.…”

Section: Discussionmentioning

confidence: 68%

“…In a previous study (Bell, Congiu, Hardy & Wintour, 1984) it was established that there is a gestational trend in the release of antidiuretic hormone (ADH) by the ovine fetus in response to the osmotic stress induced by maternal water deprivation. The fetal plasma ADH concentration, [ADH], was significantly greater, at a given plasma osmolality, in mature (126-144 d gestation) than immature (107-119 d) fetuses.…”

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confidence: 99%

The Effect of Maternal Water Deprivation on Ovine Fetal Blood Volume

Bell¹,

Wintour²

1985

Exp Physiol

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SUMMARYFetal blood volume was measured in pregnant ewes bearing chronically cannulated fetuses in the last third of gestation. The increase in fetal blood volume secondary to growth was established from serial measurements in four control animals. The effect ofmaternal dehydration was assessed by measuring the change in fetal blood volume during twelve episodes of maternal water deprivation in another six ewes. Fetal blood volume increased during each episode of maternal dehydration. In five experiments the rate of increase was greater than controls and in seven experiments the rate of increase was less than controls. Thus, fetal hypovolaemia does not occur during maternal dehydration in the ovine fetus in the last third of gestation.

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Gestation‐dependent Aspects of the Response of the Ovine Fetus to the Osmotic Stress Induced by Maternal Water Deprivation

Cited by 32 publications

References 15 publications

Fetal Rehydration Via Intraamniotic Fluid: Contribution of Fetal Swallowing

Fetal Rehydration Via Intraamniotic Fluid: Contribution of Fetal Swallowing

Action of Atrial Natriuretic Peptide in the Immature Ovine Kidney

The Effect of Maternal Water Deprivation on Ovine Fetal Blood Volume

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