Changes in water and electrolyte balance, plasma volume and composition during pregnancy in the rat.

Atherton, John C.; Dark, J M; Garland, Hugh; Morgan, M R; Pidgeon, J; Soni, S

doi:10.1113/jphysiol.1982.sp014330

Cited by 114 publications

(65 citation statements)

References 24 publications

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“…It was accentuated in late pregnancy after gestational day 14, when the plasma volume usually increases in rat pregnancies 26. This observation is in line with findings in mice with a less stringent HS diet, in which fetal growth and placental hypoxia were improved without increasing maternal BP 11.…”

Section: Discussionsupporting

confidence: 88%

Physiological and Molecular Responses to Altered Sodium Intake in Rat Pregnancy

Eisele

Klossner

Escher

et al. 2018

JAHA

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BackgroundIn pregnancy, a high plasma volume maintains uteroplacental perfusion and prevents placental ischemia, a condition linked to elevated maternal blood pressure (BP). Reducing BP by increasing Na+ intake via plasma volume expansion appears contra‐intuitive. We hypothesize that an appropriate Na+ intake in pregnancy reduces maternal BP and adapts the renin‐angiotensin system in a pregnancy‐specific manner.Methods and Results BP was measured by implanted telemetry in Sprague‐Dawley rats before and throughout pregnancy. Pregnant and nonpregnant animals received either a normal‐salt (0.4%; NS), high‐salt (8%; HS), or low‐salt (0.01%; LS) diet, or HS (days 1–14) followed by LS (days 14–20) diet (HS/LS). Before delivery (day 20), animals were euthanized and organs collected. Food, water, and Na+ intake were monitored in metabolic cages, and urinary creatinine and Na+ were analyzed. Na+ intake and retention increased in pregnancy (NS, LS), leading to a positive Na+ balance (NS, LS). BP was stable during LS, but reduced in HS conditions in pregnancy. The renin‐angiotensin system was adapted as expected. Activating cleavage of α‐ and γ‐subunits of the renal epithelial Na+ channel and expression of‐full length medullary β‐subunits, accentuated further in all LS conditions, were upregulated in pregnancy.ConclusionsPregnancy led to Na+ retention adapted to dietary changes. HS exposure paradoxically reduced BP. Na+ uptake while only modestly linked to the renin‐angiotensin system is enhanced in the presence of posttranslational renal epithelial Na+ channel modifications. This suggests (1) storage of Na+ in pregnancy upon HS exposure, bridging periods of LS availability; and (2) that potentially non–renin‐angiotensin–related mechanisms participate in ENaC activation and consecutive Na+ retention.

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Section: Discussionsupporting

confidence: 88%

Physiological and Molecular Responses to Altered Sodium Intake in Rat Pregnancy

Eisele

Klossner

Escher

et al. 2018

JAHA

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“…Pregnancy is also characterized by renal hemodynamic changes, including increased glomerular filtration rate (7) and increased proximal tubule length (1). Creatinine clearance, as a measure of glomerular filtration rate, increases during midgestation and falls significantly in late gestation in the present study, confirming previous findings (6).…”

Section: Discussionsupporting

confidence: 82%

“…The present study also confirms previous reports demonstrating increased water intake (1,4,9) and food consumption (16,21) during gestation. In fact, a decrease in the osmotic threshold for drinking as well as for AVP secretion is necessary to maintain the new steady state of fluid homeostasis.…”

Section: Discussionsupporting

confidence: 82%

“…In fact, a decrease in the osmotic threshold for drinking as well as for AVP secretion is necessary to maintain the new steady state of fluid homeostasis. In our study, the 6-ml increase in intake over excretion at the 19th day of gestation compared with nonpregnant controls indicates that the pregnant animals are in positive fluid balance, which agrees with the previous report characterizing water balance in pregnant rats by Atherton et al (1). In general, ANG-(1-7) is not regarded as a dispsogen (12).…”

Section: Discussionsupporting

confidence: 81%

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Angiotensin-(1-7) serves as an aquaretic by increasing water intake and diuresis in association with downregulation of aquaporin-1 during pregnancy in rats

Joyner¹,

Neves²,

Stovall³

et al. 2008

American Journal of Physiology-Regulatory, Integrative and Comp

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Joyner J, Neves LAA, Stovall K, Ferrario CM, Brosnihan KB. Angiotensin-(1-7) serves as an aquaretic by increasing water intake and diuresis in association with downregulation of aquaporin-1 during pregnancy in rats. Am J Physiol Regul Integr Comp Physiol 294: R1073-R1080, 2008. First published January 9, 2007 doi:10.1152/ajpregu.00572.2007.-We previously demonstrated that kidney and urine levels of angiotensin-(1-7) [ANG-(1-7)] were increased in pregnancy. To explore the role of ANG-(1-7) on fluid and electrolyte homeostasis during pregnancy, we evaluated the effect of the ANG-(1-7) antagonist D-alanine-[ANG-(1-7)] (A-779) on kidney function. Virgin and pregnant rats received infusion of vehicle or A-779 (48 g ⅐ kg Ϫ1 ⅐ h Ϫ1 ) for 8 days by osmotic minipumps. Metabolic studies were done on treatment day 7-8. Virgin and pregnant rats at day 15 and 19 were killed, and blood and kidneys were collected. Kidneys were prepared for Western blot analysis for aquaporin-1 (AQP1) and aquaporin-2. In virgin female rats, A-779 increased urine volume and decreased urinary osmolality and AQP1 with no change in water intake. In 19-day pregnant rats, A-779 significantly decreased water intake and urine volume and increased urinary osmolality and kidney AQP1 expression. Only in late gestation did A-779 treatment decrease the difference between intake and output (balance). A-779 treatment increased plasma vasopressin in late gestation but did not change vasopressin in virgins. In virgin and pregnant animals, A-779 administration had no effect on blood pressure, plasma volume, blood volume, or urinary electrolytes. These results suggest that ANG-(1-7) produces antidiuresis associated with upregulation of AQP1 in virgin rats, whereas ANG-(1-7) produces diuresis in late gestation with downregulation of AQP1. ANG-(1-7) contributes to the enhanced water intake during pregnancy, allowing maintenance of the normal volume-expanded state despite diuresis produced in part by decreased AVP and AQP1. renin-angiotensin system; pregnancy; angiotensin-(1-7); D-alanine-[angiotensin-(1-7)]; D-alanine; aquaporin; vasopressin NORMAL PREGNANCY IS A physiological condition characterized by hemodynamic change, including increased cardiac output and hypervolemia, decreased total peripheral resistance, and decreased or normal blood pressure (2). The renin angiotensin system (RAS), which is involved in blood pressure regulation and salt and fluid homeostasis, is markedly increased during pregnancy, as evidenced by increased circulating concentration of angiotensinogen, renin activity, and angiotensin II (ANG II; see Refs. 2,5,and 20). Also, increased during normal pregnancy is angiotensin-(1-7) [ANG-(1-7)], the active vasodilator of the RAS. Urinary excretion of ANG-(1-7) rises progressively during human pregnancy to levels that are 20-fold higher by the end of gestation compared with the normal menstrual cycle (35). Urinary ANG-(1-7) concentration is also increased with gestation in rats (22). ANG-(1-7), along with its forming enzyme angiotensin conver...

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“…This BP reduction is consequent to reduced vascular peripheral resistance associated with decreased influence of vasoconstrictor stimuli (3,9,10,34,37). These changes occur despite increases in blood volume and cardiac output and activation of the renin-angiotensin-aldosterone (RAA) system (2,10,39). In humans, by the sixth week of gestation, plasma renin activity (PRA) and aldosterone levels are already elevated and rise until term (10).…”

mentioning

confidence: 99%

Mineralocorticoids participate in the reduced vascular reactivity of pregnant rats

Provencher

Houde

Brochu

et al. 2012

American Journal of Physiology-Heart and Circulatory Physiology

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The renin-angiotensin-aldosterone (RAA) system is markedly activated in pregnancy. We evaluated if mineralocorticoid receptors (MR), a major component of the RAA system, are involved in the reduced vascular reactivity associated with pregnancy. Canrenoate (MR antagonist; 20 mg·kg Ϫ1 ·day Ϫ1 ) was administered to nonpregnant (NP) rats for 7 days and to pregnant rats from day 15 to 22 of gestation. These were killed on day 17, 19, or 22 of gestation and, for NP rats, after 7 days treatment. Constrictor responses to phenylephrine (PhE) and KCl were measured in endothelium-denuded thoracic aortic rings under the influence of modulators of potassium (activators) and calcium (blocker) channels. Responses to the constrictors were blunted from days 17 to 22 of gestation. Although canrenoate increased responses to PhE and KCl, it did not reverse their blunted responses in gestation. NS-1619 and cromakalim (respectively, highconductance calcium-activated potassium channels and ATP-sensitive potassium channel activators) diminished responses to both PhE and KCl. Inhibition by NS-1619 on responses to both agonists was decreased under canrenoate treatment in NP, but the reduced influence of NS-1619 during gestation was reversed by the mineralocorticoid antagonist. Cromakalim reduced the response to PhE significantly in the pregnant groups; this effect was enhanced by canrenoate. Finally, nifedipine (calcium channel blocker) markedly reduced KCl responses but to a lesser extent at the end of pregnancy, an inhibiting effect that was increased with canrenoate treatment. These data demonstrate that treating rats with a MR antagonist increased vascular reactivity but that it differentially affected potassium and calcium channel activity in aortas of NP and pregnant animals. This suggests that aldosterone is one of the components involved in vascular adaptations to pregnancy. potassium canrenoate; renin angiotensin aldosterone system; voltagedependent calcium channels; ATP-sensitive potassium channels; highconductance calcium-activated potassium channels IN HUMANS, arterial blood pressure (BP) decreases early in pregnancy, reaching a nadir during the second trimester (10, 26), whereas in rats it is stable until day 17 of gestation to decline gradually until term (day 23) (4, 37). This BP reduction is consequent to reduced vascular peripheral resistance associated with decreased influence of vasoconstrictor stimuli (3, 9, 10, 34, 37). These changes occur despite increases in blood volume and cardiac output and activation of the renin-angiotensin-aldosterone (RAA) system (2, 10, 39). In humans, by the sixth week of gestation, plasma renin activity (PRA) and aldosterone levels are already elevated and rise until term (10).In pregnant rats, PRA is increased early in gestation while aldosterone levels raise from midpregnancy until term (7, 18). In conditions other than pregnancy, such increases of the RAA system are associated with hypertension. This renders paradoxical the role of heightened RAA system in pregnancy (36).We have report...

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Changes in water and electrolyte balance, plasma volume and composition during pregnancy in the rat.

Cited by 114 publications

References 24 publications

Physiological and Molecular Responses to Altered Sodium Intake in Rat Pregnancy

Physiological and Molecular Responses to Altered Sodium Intake in Rat Pregnancy

Angiotensin-(1-7) serves as an aquaretic by increasing water intake and diuresis in association with downregulation of aquaporin-1 during pregnancy in rats

Mineralocorticoids participate in the reduced vascular reactivity of pregnant rats

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