scholarly journals Increased renal α-epithelial sodium channel (ENAC) protein and increased ENAC activity in normal pregnancy

2010 ◽  
Vol 299 (5) ◽  
pp. R1326-R1332 ◽  
Author(s):  
Crystal West ◽  
Zheng Zhang ◽  
Geoffrey Ecker ◽  
Shyama M. E. Masilamani
Keyword(s):  
Plasma Volume ◽  
Late Pregnancy ◽  
Normal Pregnancy ◽  
In Vivo Studies ◽  
Volume Status ◽  
Plasma Volume Expansion ◽  
Pregnant Rats ◽  
Mineralocorticoid Receptor Antagonist ◽  
The Difference

Pregnancy-mediated sodium (Na) retention is required to provide an increase in plasma volume for the growing fetus. The mechanisms responsible for this Na retention are not clear. We first used a targeted proteomics approach and found that there were no changes in the protein abundance compared with virgin rats of the β or γ ENaC, type 3 Na+/H+ exchanger (NHE3), bumetanide-sensitive cotransporter (NKCC2), or NaCl cotransporter (NCC) in mid- or late pregnancy. In contrast, we observed marked increases in the abundance of the α-ENaC subunit. The plasma volume increased progressively during pregnancy with the greatest plasma volume being evident in late pregnancy. ENaC inhibition abolished the difference in plasma volume status between virgin and pregnant rats. To determine the in vivo activity of ENaC, we conducted in vivo studies of rats in late pregnancy ( days 18–20) and virgin rats to measure the natriuretic response to ENaC blockade (with benzamil). The in vivo activity of ENaC (UNaV postbenzamil-UNaV postvehicle) was markedly increased in late pregnancy, and this difference was abolished by pretreatment with the mineralocorticoid receptor antagonist, eplerenone. These findings demonstrate that the increased α-ENaC subunit of pregnancy is associated with an mineralocorticoid-dependent increase in ENaC activity. Further, we show that ENaC activity is a major contributor of plasma volume status in late pregnancy. These changes are likely to contribute to the renal sodium retention and plasma volume expansion required for an optimal pregnancy.

Renal interstitial hydrostatic pressure and natriuretic responses to volume expansion in pregnant rats

2002 ◽  
Vol 282 (5) ◽  
pp. F821-F825 ◽  
Author(s):  
Ali A. Khraibi ◽  
Michael J. Solhaug ◽  
Anca D. Dobrian ◽  
Theresa J. Berndt
Keyword(s):  
Hydrostatic Pressure ◽  
Plasma Volume ◽  
Volume Expansion ◽  
Maximum Level ◽  
Fractional Excretion ◽  
Normal Pregnancy ◽  
Sprague Dawley ◽  
Plasma Volume Expansion ◽  
Pregnant Rats ◽  
Fractional Excretion Of Sodium

During normal pregnancy, a gradual plasma volume expansion (VE) occurs and reaches a maximum level at late term. Pressure natriuresis and renal interstitial hydrostatic pressure (RIHP) responses are attenuated in pregnant rats. Also, basal RIHP is lower in pregnant rats, suggesting an increase in renal interstitial compliance during pregnancy. This adaptation may contribute to the increase in plasma volume that is required for a normal pregnancy, because increases in RIHP have been consistently shown to produce natriuresis and diuresis. Acute saline VE (5% body wt/30 min) has been shown to increase RIHP in normal nonpregnant rats. Therefore, the objective of this study was to determine RIHP, natriuretic, and diuretic responses to VE in nonpregnant ( n = 7), midterm pregnant ( n = 8), and late-term pregnant ( n = 8) Sprague-Dawley rats. Although VE significantly increased RIHP, fractional excretion of sodium (FENa), and urine flow rate (V˙) in all groups, ΔRIHP was highest for nonpregnant (3.0 ± 0.3 mmHg) compared with midterm pregnant (1.6 ± 0.1 mmHg; P < 0.05 vs. nonpregnant) and late-term pregnant rats (1.2 ± 0.1 mmHg; P < 0.05 vs. both midterm pregnant and nonpregnant rats). ΔFENa and ΔV˙ were similar in all groups: 5.8 ± 1.0% and 231 ± 27 μl/min for nonpregnant, 6.8 ± 1.3% and 173 ± 16 μl/min for midterm pregnant, and 7.6 ± 1.2% and 203 ± 10 μl/min for late-term pregnant rats, respectively. In conclusion, basal RIHP and the increase in RIHP during VE were attenuated during pregnancy; however, the natriuretic and diuretic responses to VE remain intact during the course of pregnancy.

scholarly journals (Pro)renin receptor contributes to pregnancy-induced sodium-water retention in rats via activation of intrarenal RAAS and α-ENaC

2019 ◽  
Vol 316 (3) ◽  
pp. F530-F538 ◽  
Author(s):  
Ziwei Fu ◽  
Jiajia Hu ◽  
Li Zhou ◽  
Yanting Chen ◽  
Mokan Deng ◽  
...  
Keyword(s):  
Angiotensin Ii ◽  
Plasma Volume ◽  
Water Retention ◽  
Late Pregnancy ◽  
Renin Activity ◽  
Physiological Status ◽  
Sprague Dawley ◽  
Plasma Volume Expansion ◽  
Pregnant Rats ◽  
Renin Angiotensin

The (pro)renin receptor (PRR) is a new component of the renin-angiotensin-aldosterone system (RAAS) and regulates renin activity. The objective of the present study was to test potential roles of the renal PRR and intrarenal RAAS in the physiological status of late pregnancy. Late pregnant Sprague-Dawley rats were studied 19–21 days after sperm was observed in vaginal smears. Experiments were performed using age-matched virgin rats and late pregnant rats treated with the specific PRR inhibitor PRO20 (700 μg·kg−1·day−1 sc for 14 days, 3 times/day for every 8 h) or vehicle. The indices of RAAS, including PRR, renin, angiotensin II, and aldosterone levels, were examined by immunoblotting, qRT-PCR, or ELISA. Further analyses of renal epithelial sodium channel (ENaC) expression, sodium-water retention, and plasma volume were performed. We first present evidence for the activation of intrarenal RAAS in late pregnant rats, including increases in urinary renin activity, active and total renin content, and prorenin content, angiotensin II and aldosterone excretion, in parallel with increased renal PRR expression and urinary soluble PRR excretion. Functional evidence demonstrated that PRR antagonism with PRO20 effectively suppressed the indices of intrarenal RAAS in late pregnant rats. In addition, our results revealed that renal α-ENaC expression, sodium-water retention, and plasma volume were elevated during late pregnancy, which were all attenuated by PRO20. In summary, the present study examined the renal mechanism of sodium-water retention and plasma volume expansion in late pregnant rats and identified a novel role of PRR in regulation of intrarenal RAAS and α-ENaC and thus sodium and fluid retention associated with pregnancy.

Renal effects of moderate hemorrhage in the conscious pregnant rat

1990 ◽  
Vol 259 (6) ◽  
pp. F945-F949 ◽  
Author(s):  
C. Baylis ◽  
C. Brango ◽  
K. Engels
Keyword(s):  
Plasma Volume ◽  
Volume Expansion ◽  
Late Pregnancy ◽  
Total Blood Volume ◽  
Electrolyte Excretion ◽  
Plasma Volume Expansion ◽  
Total Blood ◽  
Pregnant Rats ◽  
Renal Vascular ◽  
Baseline State

Studies were performed in conscious, chronically catheterized virgin, 8- to 9-day-pregnant, and 15- to 16-day-pregnant Sprague-Dawley rats in baseline state and after removal of 7.5% total blood volume. Measurements were made of glomerular filtration rate (GFR), renal plasma flow (RPF), renal vascular resistance (RVR), arterial blood pressure (AP), and urinary electrolyte excretion. In baseline state, GFR and RPF were elevated at days 8-9 and days 15-16 of pregnancy (vs. virgins) due to a gestational renal vasodilation. The fall in hematocrit indicates substantial plasma volume expansion by days 15-16 of pregnancy. After removal of 7.5% total blood volume, little change occurred in AP in any group. However, the renal vasculature provided a sensitive response to moderate hemorrhage, since RPF fell and RVR increased similarly in virgin, 8- to 9-day- and 15- to 16-day-pregnant rats. GFR was protected in virgin and 8- to 9-day-pregnant rats but fell significantly in late pregnancy. Urinary electrolyte excretion tended to fall but was not significantly reduced by hemorrhage in any group. These studies indicate that renal vascular response to moderate hemorrhage is similar in virgin, early, and late pregnancy. Thus effector mechanisms that sense volume and regulate RVR must be continually reset to respond to progressive plasma volume expansion of pregnancy as normal.

Exercise stroke volume relative to plasma-volume expansion

1988 ◽  
Vol 64 (1) ◽  
pp. 404-408 ◽  
Author(s):  
M. K. Hopper ◽  
A. R. Coggan ◽  
E. F. Coyle
Keyword(s):  
Stroke Volume ◽  
Plasma Volume ◽  
Volume Expansion ◽  
Peripheral Resistance ◽  
Submaximal Exercise ◽  
Upright Position ◽  
Plasma Volume Expansion ◽  
Trained Subjects ◽  
The Difference ◽  
Dextran Solution

The effects of plasma-volume (PV) expansion on stroke volume (SV) (CO2 rebreathing) during submaximal exercise were determined. Intravenous infusion of 403 +/- 21 ml of a 6% dextran solution before exercise in the upright position increased SV 11% (i.e., 130 +/- 6 to 144 +/- 5 ml; P less than 0.05) in untrained males (n = 7). Further PV expansion (i.e., 706 +/- 43 ml) did not result in a further increase in SV (i.e., 145 +/- 4 ml). SV was somewhat higher during supine compared with upright exercise when blood volume (BV) was normal (i.e., 138 +/- 8 vs. 130 +/- 6 ml; P = 0.08). PV expansion also increased SV during exercise in the supine position (i.e., 138 +/- 8 to 150 +/- 8 ml; P less than 0.05). In contrast to these observations in untrained men, PV expansion of endurance-trained men (n = 10), who were naturally PV expanded, did not increase SV during exercise in the upright or supine positions. When BV in the untrained men was increased to match that of the endurance-trained subjects, SV was observed to be 15% higher (165 +/- 7 vs. 144 +/- 5 ml; P less than 0.05), whereas mean blood pressure and total peripheral resistance were significantly lower (P less than 0.05) in the trained compared with untrained subjects during upright exercise at a similar heart rate. The present findings indicate that exercise SV in untrained men is preload dependent and that increases in exercise SV occur in response to the first 400 ml of PV expansion. It appears that approximately one-half of the difference in SV normally observed between untrained and highly endurance-trained men during upright exercise is due to a suboptimal BV in the untrained men.

scholarly journals Chronic vasodilation increases renal medullary PDE5A and α-ENaC through independent renin-angiotensin-aldosterone system pathways

2013 ◽  
Vol 305 (10) ◽  
pp. R1133-R1140 ◽  
Author(s):  
Crystal A. West ◽  
Stefan Shaw ◽  
Jennifer M. Sasser ◽  
Andrea Fekete ◽  
Tyler Alexander ◽  
...  
Keyword(s):  
Plasma Volume ◽  
Enzyme Inhibitor ◽  
Virgin Female ◽  
Normal Pregnancy ◽  
Female Rats ◽  
Plasma Volume Expansion ◽  
Renin Angiotensin Aldosterone System ◽  
Α Subunit ◽  
Renin Angiotensin

We have previously observed that many of the renal and hemodynamic adaptations seen in normal pregnancy can be induced in virgin female rats by chronic systemic vasodilation. Fourteen-day vasodilation with sodium nitrite or nifedipine (NIF) produced plasma volume expansion (PVE), hemodilution, and increased renal medullary phosphodiesterase 5A (PDE5A) protein. The present study examined the role of the renin-angiotensin-aldosterone system (RAAS) in this mechanism. Virgin females were treated for 14 days with NIF (10 mg·kg−1·day−1 via diet), NIF with spironolactone [SPR; mineralocorticoid receptor (MR) blocker, 200–300 mg·kg−1·day−1 via diet], NIF with losartan [LOS; angiotensin type 1 (AT1) receptor blocker, 20 mg·kg−1·day−1 via diet], enalapril (ENAL; angiotensin-converting enzyme inhibitor, 62.5 mg/l via water), or vehicle (CON). Mean arterial pressure (MAP) was reduced 7.4 ± 0.5% with NIF, 6.33 ± 0.5% with NIF + SPR, 13.3 ± 0.9% with NIF + LOS, and 12.0 ± 0.4% with ENAL vs. baseline MAP. Compared with CON (3.6 ± 0.3%), plasma volume factored for body weight was increased by NIF (5.2 ± 0.4%) treatment but not by NIF + SPR (4.3 ± 0.3%), NIF + LOS (3.6 ± 0.1%), or ENAL (4.0 ± 0.3%). NIF increased PDE5A protein abundance in the renal inner medulla, and SPR did not prevent this increase (188 ± 16 and 204 ± 22% of CON, respectively). NIF increased the α-subunit of the epithelial sodium channel (α-ENaC) protein in renal outer (365 ± 44%) and inner (526 ± 83%) medulla, and SPR prevented these changes. There was no change in either PDE5A or α-ENaC abundance vs. CON in rats treated with NIF + LOS or ENAL. These data indicate that the PVE and renal medullary adaptations in response to chronic vasodilation result from RAAS signaling, with increases in PDE5A mediated through AT1 receptor and α-ENaC through the MR.

scholarly journals Hormonal control of Luteal 20α-Hydroxy steroid dehydrogenase and Δ5-3β-hydroxy steroid dehydrogenase during luteolysis in the pregnant rat

1975 ◽  
Vol 152 (3) ◽  
pp. 433-443 ◽  
Author(s):  
R G Rodway ◽  
N J Kuhn
Keyword(s):  
Prostaglandin F2α ◽  
Late Pregnancy ◽  
Normal Pregnancy ◽  
Hormonal Control ◽  
Placental Lactogen ◽  
Pregnant Rats ◽  
Pregnant Rat ◽  
Hydroxy Steroid ◽  
Steroid Dehydrogenase

Treatment of pregnant rats with human chorionic gonadotrophin, luteotrophin (luteinizing hormone), luteotrophin-releasing hormone, prostaglandin F2α, aminoglutethimide, or by foetoplacental removal or hysterectomy achieved a common multiple-response pattern, namely increased activity of luteal 20α-hydroxy steroid dehydrogenase with decreased activity of delta5-3β-hydroxy steriod dehydrogenase and release of delta4-3-oxo steroids in vitro. 2. Similar effects of foetoplacental removal are noted in pregnant mice. 3. Gonadotrophin induced lower activities of 20α-hydroxy steroid dehydrogenase, except at the very end of pregnancy, and partly inhibited the induction caused by foetoplacental removal. 4. The results suggest that existence of a placental factor that restrains these changes until the end of normal pregnancy, which is produced in amounts proportional to the number of placentae and is conveyed to the ovary via the blood. 5. This factor was not replaced by prolactin. 6. It is argued that neither placental lactogen nor pituitary luteotrophin participate in the induction of 20α-hydroxy steroid dehydrogenase at late pregnancy in the rat. 7. Aminoglutethimide induced 20α-hydroxy steroid dehydrogenase only in late pregnancy. This was partly reversed by progesterone, wholly reversed by progesterone plus oestrogen, and did not involve the pituitary.

Pregnancy Does Not Increase Susceptibility to Bupivacaine in Spinal Root Axons

1997 ◽  
Vol 87 (3) ◽  
pp. 610-616 ◽  
Author(s):  
Friederike B. Dietz ◽  
Richard A. Jaffe
Keyword(s):  
Conduction Block ◽  
Late Pregnancy ◽  
Underlying Mechanism ◽  
Ventral Root ◽  
Spinal Root ◽  
Pregnant Rats ◽  
C Fibers ◽  
Antinociceptive Effects ◽  
The Difference

Background The underlying mechanism of enhanced antinociceptive effects and increased susceptibility to local anesthetics during pregnancy is not known. Mechanical, hormonal, biochemical, and neural changes have been suggested. The authors measured the susceptibility of individual spinal root axons to bupivacaine during late pregnancy in rats and compared them with similar measurements in nonpregnant rats. Methods Lumbar dorsal and ventral roots were excised from anesthetized pregnant and nonpregnant rats. Single-fiber dissection and recording techniques were used to isolate activity in individual axons. Supramaximal constant voltage stimuli were delivered to the distal end of the root. During in vitro perfusion, each root was exposed to increasing concentrations of bupivacaine, and the minimum blocking concentration (Cm) and the concentration that increased conduction latency by 50% (EC50) were measured. Results Myelinated and unmyelinated dorsal and ventral root axons of pregnant rats appeared to be less sensitive to steady-state conduction block and to the latency-increasing effects of bupivacaine than were equivalent axons from nonpregnant rats. Although when comparing specific axon types, only the difference in C-fibers was significant (Cm = 29.8 microM for pregnant and Cm = 22.1 microM for nonpregnant rats, P &lt; 0.05; EC50 = 19.9 microM and 13.6 microM, respectively). Conclusions In contrast to clinical expectations, the susceptibility to bupivacaine conduction block in individual dorsal and ventral root axons during late pregnancy in rats was not greater in pregnant animals. Pregnancy-related changes in diffusion barriers and activation of endogenous analgesic systems without changes in the electrophysiologic properties of spinal root axons are suggested as possible explanations for the discrepancy between clinical and experimental observations.

Localization and regulation of IL-1α in rat myometrium during late pregnancy and the postpartum period

2001 ◽  
Vol 280 (3) ◽  
pp. R879-R888 ◽  
Author(s):  
J. Andres Melendez ◽  
James M. Vinci ◽  
John J. Jeffrey ◽  
Brian D. Wilcox
Keyword(s):  
Postpartum Period ◽  
Preterm Labor ◽  
Interleukin 1 ◽  
Late Pregnancy ◽  
Mrna Levels ◽  
Pregnant Rats ◽  
Low Levels ◽  
Interstitial Collagenase

Interleukin-1 (IL-1) has been implicated as a participant in preterm labor that is induced by bacterial infection. Previously, we showed that serotonin-induced production of IL-1α by myometrial smooth muscle cells in vitro is also essential for the synthesis of interstitial collagenase. It is therefore likely that IL-1α production in uterine tissues has implications for both the normal physiology of involution and for the pathophysiological mechanisms of preterm labor. The objective of this study was to characterize the serotonin-induced production of IL-1α by myometrial cultures in vitro and to assess the production of IL-1α and its relationship to collagenase production in vivo during pregnancy and the postpartum period. Immunohistochemistry demonstrated IL-1α protein in the nuclei and cytoplasm of serotonin-treated myometrial cells. IL-1α levels were decreased by treatment with progesterone or IL-1-receptor antagonist but were unaffected by lipopolysaccharide. Western analysis of myometrium from pregnant rats showed low levels of IL-1α during midpregnancy with increased concentrations at days 21 and 22 and postpartum. IL-1α mRNA levels also increased from days 15to 22. Levels of mRNA for IL-1β also increased, although to a lesser degree than IL-1α. Both mRNAs decreased postpartum. Conversely, mRNA for interstitial collagenase was barely detectable at term but increased postpartum. Together, these data show that serotonin stimulates IL-1α production in vitro and indicate that normal myometrium from pregnant rats is an identifiable source of IL-1 during late pregnancy. The findings are consistent with the possibility that myometrial IL-1α participates in normal labor as well as the postpartum production of interstitial collagenase.

Renal cortical Na+-K+-ATPase activity and abundance is decreased in normal pregnant rats

1998 ◽  
Vol 275 (5) ◽  
pp. F812-F817 ◽  
Author(s):  
J. Mahaney ◽  
C. Felton ◽  
D. Taylor ◽  
W. Fleming ◽  
J. Q. Kong ◽  
...  
Keyword(s):  
Atpase Activity ◽  
Brain Stem ◽  
Renal Cortex ◽  
Renal Medulla ◽  
Late Pregnancy ◽  
Sodium Retention ◽  
Plasma Volume Expansion ◽  
Pregnant Rats ◽  
Small Rise ◽  
Α1 Subunit

During late pregnancy, the rat undergoes massive plasma volume expansion due to cumulative renal sodium retention. In the present study, conducted in virgin, mid- ( days 11–13), and late-pregnant ( days 18–20) rats, we measured both Na+-K+-ATPase activity (by coupled enzyme assay) and abundance of the α-subunits of the Na+-K+-ATPase (by Western and slot blot analyses) in renal cortex, medulla, and brain stem. Unexpectedly, Na+-K+-ATPase in renal cortex, in both stages of pregnancy, is reduced versus the virgin, consistent with our finding of a reduced quantity of the α1-subunit. In renal medulla, there is a small rise in activity at midterm, but there is no difference in either activity or abundance of the α1-subunit in late pregnancy, when renal Na retention is maximal. In brain stem, where only α2- and α3-subunits are evident, pregnancy has no impact on enzyme activity or abundance of either isoform. In conclusion, the outcome of these experiments was unexpected in that we did not observe increased renal Na+-K+-ATPase activity in late pregnancy in the rat. In fact, in renal cortex, Na+-K+-ATPase activity and abundance are reduced. Whatever promotes net sodium retention in pregnancy must be capable of overwhelming this and several other strong natriuretic signals.

scholarly journals Effect of insulin on glucose metabolism in adipocytes from virgin and late-pregnant rats

1984 ◽  
Vol 224 (2) ◽  
pp. 685-688 ◽  
Author(s):  
A Leturque ◽  
M Guerre-Millo ◽  
M Lavau ◽  
J Girard
Keyword(s):  
Glucose Metabolism ◽  
High Sensitivity ◽  
Late Pregnancy ◽  
Maximal Response ◽  
Maximal Effect ◽  
Insulin Stimulation ◽  
Response Curves ◽  
Pregnant Rats

Under basal conditions (zero insulin), paraovarian adipocytes from 19-day-pregnant rats exhibited the same rates of [U-14C]glucose conversion into CO2 and total lipids as did those from age-matched virgin rats. The dose-response curves for insulin stimulation of glucose metabolism were similar in both groups: maximal response (+100% over basal values) and high sensitivity (half-maximal effect at 0.05 nM-insulin). The present results suggest that the insulin resistance in vivo that occurs during late pregnancy may involve circulating factors lost in vitro.

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