Osmotic flow through the placental barrier of chronically prepared sheep

Armentrout, T.; Katz, Schmuel; Thornburg, Kent L.; Faber, J. Job

doi:10.1152/ajpheart.1977.233.4.h466

Cited by 39 publications

(36 citation statements)

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“…Fetal plasma AVP levels did not change in response to the under aerobic conditions (10). More precise determinations un-intraamniotic rehydration.…”

Section: Fetal Rehydration (Intraamniotic)mentioning

confidence: 81%

“…der anaerobic conditions, which reduce plasma carbon diox-rehydration resulted in decreased fetal plasma osmolality but a ide loss, indicate actual plasma osmolality gradients of 2 to 3 continued elevation of plasma AVP (5). As dehydration-induced mosmol/kg (10). Despite ad libitum feeding, postprandial fetal blood volume contraction was not normalized by maternal changes in maternal plasma osmolality (1 1) also may have con-rehydration in the prior study, it suggested that AVP secretion tributed to the observed basal osmotic gradient.…”

Section: Fetal Rehydration (Intraamniotic)mentioning

confidence: 96%

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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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“…Fetal plasma AVP levels did not change in response to the under aerobic conditions (10). More precise determinations un-intraamniotic rehydration.…”

Section: Fetal Rehydration (Intraamniotic)mentioning

confidence: 81%

Section: Fetal Rehydration (Intraamniotic)mentioning

confidence: 96%

Fetal Rehydration Via Intraamniotic Fluid: Contribution of Fetal Swallowing

et al. 1991

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“…Arterial blood gases were measured using an IL pHblood gas analyzer (micro 13, Instrumentation Laboratory, Lexington, MA) or a CIBA-Corning blood gas system (model 288, Medfield, MA). Plasma bicarbonate concentration was calculated using a modified Henderson-Hasselbach equation (10). Hematocrit was measured in duplicate using a hematocrit centrifuge and reader.…”

Section: Methodsmentioning

confidence: 99%

Changes in Renal Function and Blood Volume in the Newborn Lamb Delivered by Cesarean Section

Gibson

Lumbers

1994

Pediatr Res

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To determine the cause of the transient natriuresis in lambs within 1-2 h of birth, renal function and blood volume (BV) were measured in nine chronically catheterized fetal sheep aged 139-145 d before and after delivery by cesarean section. After delivery, sodium excretion increased &fold. This was due to a transient rise in glomerular filtration rate (by 39 + 21%, p < 0.02) and a fall in fractional reabsorption of sodium by the proximal tubule from 63.4 2 2.5% to 53.4 + 3.4% @ < 0.01). The distal tubule failed to compensate fully for this fall, because fractional reabsorption by the distal tubule rose from 35.5 2 2.4% to only 41.6 2 2.2% @ < 0.05). The extent of the natriuresis did not depend on the lamb's initial BV per kg at birth. However, the amount of fluid excreted and the clearance of sodium during a 45-min period within the first 1-1.25 h after birth were approximately equal to the fall in BV that occurred during this time. Thus, most of the fall in After birth, human infants have a transient increase in urine flow rate (1). Similarly, lambs delivered by cesarean section at 139-145 d have a transient natriuresis and disruption of glomerulotubular balance (2). It has been suggested that volume expansion of the newborn, resulting from placental blood transfusion, may contribute to this diuresis (3). We postulated that lambs with larger BV relative to their weights would show a greater natriuresis than lambs with smaller BV per kg body weight. It should be noted that because it was not possible to measure partitioning of the fetal BV between the fetal body and the placenta before birth, it could not be determined whether placental transfusion occurred with delivery.

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“…GFR was calculated as the renal clearance of 125 I-labeled sodium iothalamate, and fractional reabsorption of sodium by the proximal and distal nephron was calculated from the renal clearance of lithium (22). Plasma bicarbonate concentrations were calculated using a formula derived from the Henderson-Hasselbach equation (1). Filtration fraction relative to control was calculated from the formula, Filtration fraction ϭ GFR c/RBFc, where GFRc and RBFc are expressed as a percentage of their respective control values.…”

Section: Methodsmentioning

confidence: 99%

Effects of 7-day amino acid infusion on renal growth, function, and renin-angiotensin system in fetal sheep

Boyce

Gibson²,

Wintour³

et al. 2005

American Journal of Physiology-Regulatory, Integrative and Comp

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. Effects of 7-day amino acid infusion on renal growth, function, and renin-angiotensin system in fetal sheep. Am J Physiol Regul Integr Comp Physiol 289: R1099-R1106, 2005. First published June 16, 2005 doi:10.1152/ajpregu.00055.2005.-These experiments examined whether renal growth and the fetal reninangiotensin system could be stimulated by infusion of amino acids and whether chronic amino acid infusions restored glomerulotubular balance, which had been disrupted during 4-h infusions. Five fetal sheep aged 122 Ϯ 1 days gestation received an infusion of alanine, glycine, proline and serine in 0.15 M saline at 0.22 mmol/min for 7 days. Six control fetuses were given saline at the same rate (5 ml/h). Kidney wet weights after amino acid infusion were 28% larger than control fetuses (P Ͻ 0.05), and renal angiotensinogen mRNA levels were ϳ2.6-fold higher (P Ͻ 0.005). Circulating renin levels and renal renin mRNA levels were suppressed (P Ͻ 0.05), and renal renin protein levels tended to be lower. Arterial pressure was increased, and there was a marked, sustained natriuresis and diuresis. Glomerular filtration rate and filtered sodium were ϳtwo-fold higher throughout infusion (P Ͻ 0.05). Fractional proximal sodium reabsorption, suppressed at 4 h (from 73.4 Ϯ 6.5 to 53.7 Ϯ 10.2%), did not return to control levels (36.1 Ϯ 3.4% on day 7, P Ͻ 0.05). Distal sodium reabsorption was markedly increased (from 79 Ϯ 25 to 261 Ϯ 75 mol/min by day 7, P Ͻ 0.005), but this was not sufficient to restore glomerulotubular balance. The resultant high rates of sodium excretion led to hyponatremia and polyhydramnios. In conclusion, longterm amino acid infusions increased renal angiotensinogen gene expression, kidney weight, and distal nephron sodium reabsorptive capacity but failed to restore proximal and total glomerulotubular balance.fetus; renal function PROTEIN-RICH MEALS AND ACUTE intravenous amino acid infusions have a well-described stimulatory effect on renal function in adult animals and humans, increasing glomerular filtration rate (GFR), renal blood flow (RBF), and tubular reabsorption (16,41,46). Acute amino acid infusions also have marked effects on fetal renal function (26, 45). We have previously reported that during a 4-h infusion of amino acids to lategestation fetal sheep, there were large increases in GFR (50% above control levels) and filtration fraction (FF) and increases in both proximal and distal tubular sodium reabsorption that were sustained for the duration of the infusion (26).In the present study, we continued the 4-h infusion of amino acids for a further 7 days. One of our aims was to find out whether long-term infusion of amino acids would cause the fetal sheep kidney to grow. It is well described that in weanling and adult rats high-protein diets stimulate renal growth, characterized by hypertrophy and hyperplasia of the glomerulus, proximal tubule, and thick ascending limb of the loop of Henle (10, 18, 24, 43). There is evidence that this growth may be partly work induced, related to the increases in glo...

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Osmotic flow through the placental barrier of chronically prepared sheep

Cited by 39 publications

References 0 publications

Fetal Rehydration Via Intraamniotic Fluid: Contribution of Fetal Swallowing

Fetal Rehydration Via Intraamniotic Fluid: Contribution of Fetal Swallowing

Changes in Renal Function and Blood Volume in the Newborn Lamb Delivered by Cesarean Section

Effects of 7-day amino acid infusion on renal growth, function, and renin-angiotensin system in fetal sheep

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