Sodium and water reabsorption in the proximal and distal nephron in conscious pregnant rats and third trimester women.

Atherton, John C.; Bielińska, Aneta; Davison, John M.; Haddon, I; Kay, Catherine; Samuels, Rayna E.

doi:10.1113/jphysiol.1988.sp016972

Cited by 27 publications

(12 citation statements)

References 34 publications

(61 reference statements)

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“…Furthermore, plasma volume expansion found during pregnancy is associated with a rise in the glomerular filtration rate in the rat (Baylis, 1987), which in turn increases Na + filtration and reabsorption rates. Increases in Na + reabsorption are observed during gestation in both proximal tubules and distal nephrons of the rat kidney (Atherton et al 1988). In view of the above, the decrease we found in plasma urea concentration in the pregnant rats on the normal diet may be due to both extracellular fluid expansion and the decrease in P osm .…”

Section: Renal Function Osmoregulation and Angii Receptor Expressionmentioning

confidence: 50%

Modulation of body fluids and angiotensin II receptors in a rat model of intra‐uterine growth restriction

Bédard

Sicotte

St‐Louis

et al. 2005

The Journal of Physiology

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We previously reported that sodium restriction during pregnancy reduces plasma volume expansion and promotes intra-uterine growth restriction (IUGR) in rats while it activates the renin-angiotensin-aldosterone system (RAAS). In the present study, we proceeded to determine whether expression of the two angiotensin II (ANGII) receptor subtypes (AT 1 and AT 2 ) change in relation to maternal water-electrolyte homeostasis and fetal growth. To this end, pregnant (gestation day 15) and non-pregnant Sprague-Dawley rats were randomly assigned to two groups fed either normal, or Na + -restricted diets for 7 days. At the end of the treatment period, plasma aldosterone and renin activity as well as plasma and urine electrolytes were measured. Determinations for AT 1 and AT 2 mRNA and protein were made by RNase protection assay and photoaffinity labelling, respectively, using a number of tissues implicated in volume regulation and fetal growth. In non-pregnant rats, Na + restriction decreases Na + excretion without altering plasma volume, plasma Na + concentration or the expression of AT 1 and AT 2 mRNA or protein in the tissues examined. In normally fed pregnant rats when compared to non-pregnant controls, AT 1 mRNA increases in the hypothalamus as well as pituitary and declines in uterine arteries, while AT 1 protein decreases in the kidney and AT 2 mRNA declines in the adrenal cortex. In pregnant rats, Na + restriction induces a decrease in plasma Na + , an increase in plasma urea, as well as a decline in renal urea and creatinine clearance rates. Protein levels for both AT 1 and AT 2 in the pituitary and AT 2 mRNA in the adrenal cortex are lower in the Na + -restricted pregnant group when compared to normally fed pregnant animals. Na + restriction also induces a decrease in AT 1 protein in the placenta. In conclusion, these results suggest that pregnancy may increase sensitivity to Na

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Section: Renal Function Osmoregulation and Angii Receptor Expressionmentioning

confidence: 50%

Modulation of body fluids and angiotensin II receptors in a rat model of intra‐uterine growth restriction

Bédard

Sicotte

St‐Louis

et al. 2005

The Journal of Physiology

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“…Therefore, aldosterone may play a more important role in sodium homeostasis, whereas deoxycorticosterone may play a more integral role in promoting sodium retention. Finally, considering the remarkable GFR-mediated increment in sodium filtration, glomerulotubular changes are needed to ensure sodium reabsorption in the proximal and distal tubules to avoid excessive renal solute losses (70). Some authors have suggested that this may be mediated by increments in the number of renal Na1/K1 ATPase (71), but this is controversial (72).…”

Section: Electrolyte Balancementioning

confidence: 99%

Obstetric Nephrology

Odutayo

Hladunewich

2012

Clinical Journal of the American Society of Nephrology

166

106

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SummaryGlomerular hyperfiltration, altered tubular function, and shifts in electrolyte-fluid balance are among the hallmark renal physiologic changes that characterize a healthy pregnancy. These adjustments are not only critical to maternal and fetal well being, but also provide the clinical context for identifying gestational aberrations in renal function and electrolyte composition. Systemic vasodilation characterizes early gestation and produces increments in renal plasma flow and GFR, the latter of which is maintained into the postpartum period. In addition, renal tubular changes allow for the accumulation of nutrients and electrolytes necessary for fetal growth such that wasting of proteins, glucose, and amino acids in urine is limited in pregnancy and total body stores of electrolytes increase throughout gestation. Substantial insight into the mechanisms underlying these complex adjustments can be gleaned from the available animal and human literature, but our understanding in many areas remains incomplete. This article reviews the available literature on renal adaptation to normal pregnancy, including renal function, tubular function, and electrolyte-fluid balance, along with the clinical ramifications of these adjustments, the limitations of the existing literature, and suggestions for future studies.

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“…Lithium clearance studies in women have indicated enhanced sodium reabsorption in the proximal tubule and distal nephron segments in late pregnancy, whereas animal studies have been contradictory. 36 The reason for the net renal sodium retention in pregnancy is not known. As shown in Figure 41.6, there are many factors operating both to increase and to decrease sodium excretion, and exactly how the normal balance of net retention is achieved remains a mystery.…”

Section: Volume Regulationmentioning

confidence: 99%