Effect of pregnancy on rat myometrial β2-adrenoceptor mRNA and isoproterenol-induced relaxation of isolated uterine strips

1997 ◽  
Vol 153 (3) ◽  
pp. 393-399 ◽  
Author(s):  
T Engstrøm ◽  
P Bratholm ◽  
H Vilhardt ◽  
N J Christensen
Keyword(s):  
De Novo ◽  
Contractile Activity ◽  
Post Partum ◽  
Late Pregnancy ◽  
Maximal Effect ◽  
Adrenergic Stimulation ◽  
Pregnant Rats ◽  
Binding Characteristics ◽  
Near Term ◽  
One Way Anova

Abstract The altered myometrial contractile activity near term of pregnancy is partly due to changes in the responsiveness to catecholamines. Previous experiments have basically been concerned with uterine adrenoceptor binding characteristics. In the present study we have evaluated total myometrial DNA, β2-adrenoceptor mRNA and isoproterenol-induced relaxation of rat isolated uterine strips pre-contracted with potassium on days 0, 7, 14 and 21 of pregnancy and on day 5 post-partum. Total myometrial DNA expressed per milligram wet tissue peaked at day 14 of pregnancy followed by a decrease at the end of gestation. This suggests that hyperplasia predominates in the growth of the uterus in early gestation, whereas hypertrophy may be more marked in late pregnancy. The concentration of β2-adrenoceptor mRNA decreased linearly throughout the gestational period (0·73 ± 0·20 amol/mg wet tissue on day 0 vs 0·34 ± 0·09 amol/mg wet tissue on day 21, P<0·05). Five days after parturition, at which time the uterus had returned to its pre-pregnant weight, β2-adrenoceptor mRNA was found to have increased 8-fold (2·79 ± 0·14 amol/mg wet tissue, P<0·05) as compared with day 21. The maximal effect of isoproterenol on pre-contracted uterine strips in which α-receptors were blocked by phentolamine showed a similar decrease which on day 21 reached 67% of the day 0 level (P<0·001). EC50 values were unchanged in all groups except day 21 pregnant rats in which an increase was observed. One-way ANOVA with Bonferroni's t-test showed statistically significant differences only between the day 21 group and either the day 5 post-partum group or the day 14 pregnant group (P<0·05). The observed alteration in EC50 prior to the end of gestation indicates that the system becomes less sensitive to β2-adrenergic stimulation at this time. We conclude that a reduction of de novo synthesis of β2-adrenoceptors may play a role in contributing to the increased myometrial activity at term. We further suggest that the dramatic up-regulation of β2-adrenoceptor mRNA postpartum may protect the fully involuted uterus against excessive contractions induced by oxytocin secreted during lactation. Journal of Endocrinology (1997) 153, 393–399

Abstract 20385: Pregnancy-Induced Cardiac Hypertrophy is Accompanied by Unique Contractile Properties Not Seen in Other Forms of Physiological Hypertrophy

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Jessica Tyrrell ◽  
Kaitlyn Kennard ◽  
Catherine Makarewich ◽  
Beth A Bailey
Keyword(s):  
Cardiac Hypertrophy ◽  
Late Pregnancy ◽  
Calcium Transient ◽  
Contractile Properties ◽  
Receptor Protein ◽  
Ca Channel ◽  
Adrenergic Stimulation ◽  
Twitch Contraction ◽  
Relaxation Phase ◽  
Near Term

Background: Cardiac hypertrophy accompanying pregnancy has generally been categorized as physiologic hypertrophy similar to that seen with exercise, however a reduction in cardiac function in late pregnancy has been suggested. Furthermore, the hemodynamic stress of pregnancy can induce a maladaptive, pathologic hypertrophy in a small number of women. This study seeks to characterize the contractile properties of late-pregnant myocardium. Methods and Results: Late Pregnancy (LP) Female Swiss-Webster mice were bred then studied at near term (Embryonic day 17-19) and compared to age-matched, non-pregnant (NP) controls. Individual cardiac myocytes were isolated using collagenase-based perfusion technique. Two-dimensional Surface Area measured in quiescent cells was elevated (p<.01) in LP myocytes (LPM) (3609± 132u 2 ) vs NP myocytes (NPM) (2736± 88u 2 ), and this increase was due to increases in both length (8.5%) and width (15.6%). Western Blot analysis showed a reduction in Ryanodine Receptor protein in LP, but no differences in L-type Ca Channel, SERCA or Phospholamban levels. Sarcomere length (light diffraction) and Ca 2+ transients (fluo-3) were measured at pacing rates of 1 Hz and at bath [Ca] of 2mM. Duration of twitch contraction was prolonged (p<.05) in LPM as measured by Time to 75% Recovery (.42 ± .02 vs .37 ±.01 sec in NPM) and Time to 90% recovery (.51 ± .02 vs .45 ± .02 sec in NPM). There were no differences in other contractile parameters measured or in the fluo-3 calcium transient properties. 10 -7 M Isoproterenol (ISO) was used to determine the responsiveness to adrenergic stimulation. ISO induced significantly enhanced contractility in both LPM and NPM, and the response was heightened in LPM such that the presence of ISO normalized the differences in the duration of twitch contraction between LPM and NPM. Conclusions: These results suggest that hypertrophied LPM have characteristics of both physiologic and pathologic hypertrophy including enhanced responsiveness to ISO and a prolonged relaxation phase. The prolongation of relaxation is not seen in physiologic hypertrophy induced by exercise and may contribute to the diastolic dysfunction reported in some pregnancies. Enhanced response to ISO suggests an increased cardiac reserve in LPM.

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.

scholarly journals Induction of expression and phosphorylation of heat shock protein B5 (CRYAB) in rat myometrium during pregnancy and labour

Reproduction ◽  
2016 ◽  
Vol 152 (1) ◽  
pp. 69-79 ◽  
Author(s):  
J G Nicoletti ◽  
B G White ◽  
E I Miskiewicz ◽  
D J MacPhee
Keyword(s):  
Heat Shock ◽  
Protein Expression ◽  
Post Partum ◽  
Focal Adhesions ◽  
Late Pregnancy ◽  
Immunoblot Analysis ◽  
Small Molecular Weight ◽  
Pregnant Rats ◽  
Immune System Activation ◽  
Cryab Protein

During pregnancy the myometrium undergoes a programme of differentiation induced by endocrine, cellular, and biophysical inputs. Small heat shock proteins (HSPs) are a family of ten (B1–B10) small-molecular-weight proteins that not only act as chaperones, but also assist in processes such as cytoskeleton rearrangements and immune system activation. Thus, it was hypothesized that HSPB5 (CRYAB) would be highly expressed in the rat myometrium during the contractile and labour phases of myometrial differentiation when such processes are prominent. Immunoblot analysis revealed that myometrial CRYAB protein expression significantly increased from day (D) 15 to D23 (labour;P<0.05). In correlation with these findings, serine 59-phosphorylated (pSer59) CRYAB protein expression significantly increased from D15 to D23, and was also elevated 1-day post-partum (P<0.05). pSer59-CRYAB was detected in the cytoplasm of myocytes within both uterine muscle layers mid- to late-pregnancy. In unilaterally pregnant rats, pSer59-CRYAB protein expression was significantly elevated in the gravid uterine horns at both D19 and D23 of gestation compared with non-gravid horns. Co-immunolocalization experiments using the hTERT-human myometrial cell line and confocal microscopy demonstrated that pSer59-CRYAB co-localized with the focal adhesion protein FERMT2 at the ends of actin filaments as well as with the exosomal marker CD63. Overall, pSer59-CRYAB is highly expressed in myometrium during late pregnancy and labour and its expression appears to be regulated by uterine distension. CRYAB may be involved in the regulation of actin filament dynamics at focal adhesions and could be secreted by exosomes as a prelude to involvement in immune activation in the myometrium.

A quantitative study of rat uterine sympathetic innervation during pregnancy and post partum

2006 ◽  
Vol 18 (5) ◽  
pp. 525 ◽  
Author(s):  
R. Chávez-Genaro ◽  
P. Lombide ◽  
G. Anesetti
Keyword(s):  
Quantitative Study ◽  
Post Partum ◽  
Sympathetic Innervation ◽  
Glyoxylic Acid ◽  
Late Pregnancy ◽  
Uterine Horn ◽  
Pregnant Rats ◽  
Tissue Sections ◽  
Hormonal Milieu

In mammals, pregnancy induces a transient and extensive degeneration of uterine sympathetic innervation. We used the models of unilateral oviduct ligation and in oculo myometrium transplant in pregnant rats to address the role of stretching forces and/or hormone milieu in the loss of sympathetic innervation. The sympathetic fibres of the uterine horn and in oculo myometrial transplants were quantified on tissue sections processed by the glyoxylic acid technique. In normal pregnant rats, the density of uterine horn innervation was significantly reduced at late pregnancy and recovery took place during post partum. The empty horn of pregnant rats showed no significant changes in density of myometrial innervation during pregnancy or post partum. In oculo myometrial transplants were organotypically reinnervated in virgin animals. When the transplants were exposed to gestational hormonal milieu, few or no fibres were observed to the end of pregnancy; however, a significant increase at post partum was observed. Results showed that both the effects of stretching and the hormone milieu derived from the fetus–placenta complex play a role as inductors of changes on sympathetic myometrial innervation during pregnancy and support the idea that immature muscular uterine fibres are more susceptible to the effects of pregnancy than those originating from adult animals.

Serum concentrations of testosterone throughout pregnancy in rats

1982 ◽  
Vol 94 (1) ◽  
pp. 21-27 ◽  
Author(s):  
R. S. Bridges ◽  
R. B. Todd ◽  
C. M. Logue
Keyword(s):  
Post Partum ◽  
Late Pregnancy ◽  
Serum Testosterone ◽  
Serum Levels ◽  
Diurnal Variations ◽  
Serum Prolactin ◽  
Serum Concentrations ◽  
Pregnant Rats ◽  
Pregnant Rat ◽  
Microcolumn Chromatography

Testosterone concentrations in serum of rats bled throughout pregnancy and post partum were measured using Celite microcolumn chromatography and a radioimmunoassay for testosterone. Mean serum levels of testosterone ranged from about 170 to 340 pmol/l during the first 10 days of pregnancy. Significant increases in concentrations of testosterone in serum of pregnant rats were found on days 12, 15 and 18 of gestation. The highest testosterone concentrations occurred on days 18 and 20 of pregnancy when mean levels were 3228 and 3685 pmol/l respectively. Testosterone levels declined before parturition on day 22 (mean = 1449 pmol/l and declined further after parturition (mean = 315 pmol/l). In order to determine whether serum testosterone concentrations varied during the day in the pregnant rat, samples were collected at 6-h intervals on days 6–7 and 14–15 of gestation. Diurnal variations in serum testosterone concentrations were not evident during early or late pregnancy, unlike the rhythmic changes in serum prolactin levels found at these times during early pregnancy. The possible sources of the increased titres of serum testosterone during the second part of gestation in rats are discussed.

scholarly journals Expression of small heat shock-related protein 20 (HSP20) in rat myometrium is markedly decreased during late pregnancy and labour

Reproduction ◽  
2007 ◽  
Vol 133 (4) ◽  
pp. 807-817 ◽  
Author(s):  
B E Cross ◽  
H M O’Dea ◽  
D J MacPhee
Keyword(s):  
Smooth Muscle ◽  
Heat Shock ◽  
Longitudinal Muscle ◽  
Post Partum ◽  
Muscle Relaxation ◽  
Late Pregnancy ◽  
Smooth Muscle Relaxation ◽  
Pregnant Rats ◽  
Longitudinal Muscle Layer ◽  
Mrna Detection

The underlying mechanisms regulating uterine contractions during labour are still poorly understood. Heat shock protein 20 (HSP20) is known to be present at high levels in smooth muscle and implicated in muscle relaxation, but HSP20 expression in the myometrium is completely undetermined. Since HSP20 has been implicated in smooth muscle relaxation, we hypothesized that HSP20 would be highly expressed in the rat myometrium during early and mid-pregnancy when the myometrium is relatively quiescent. Northern blot analysis particularly demonstrated that HSP20 mRNA detection was significantly decreased from day (d) 22 of pregnancy to 1-daypost-partum(PP) compared with d6 (P< 0.05). HSP20 mRNA detection was also significantly decreased from d22 to d23 of gestation compared with non-pregnant (NP) samples. Immunoblot analysis showed that detection of HSP20 was significantly decreased at d23 compared with d12 and d15 (P< 0.05). HSP20 detection also significantly decreased at PP compared with d15 (P< 0.05). Immunofluorescence analysis demonstrated that after d15, plasma membrane-associated localization of HSP20 decreased markedly in both circular and longitudinal muscle layers. In addition, HSP20 was detectable near cell membranes at much higher levels in the longitudinal muscle layer of progesterone-treated pregnant rats (delayed labour) at all gestational time points examined, compared with controls. Our results demonstrate that HSP20 mRNA and protein are highly expressed during early and mid-pregnancy and then the expression markedly decreases during late pregnancy and labour. The observed patterns of HSP20 expression are consistent with a potential role for HSP20 in facilitating myometrium quiescence during early and mid-pregnancy.

OESTRADIOL CONTENT OF OVARIAN VENOUS BLOOD AND OVARIAN TISSUE IN HYPOPHYSECTOMIZED RATS DURING LATE PREGNANCY

1972 ◽  
Vol 54 (1) ◽  
pp. 79-85 ◽  
Author(s):  
H. B. WAYNFORTH ◽  
D. M. ROBERTSON
Keyword(s):  
Corpus Luteum ◽  
Post Partum ◽  
Ovarian Tissue ◽  
Venous Blood ◽  
Late Pregnancy ◽  
Corpora Lutea ◽  
Pregnant Rats ◽  
Hypophysectomized Rats ◽  
Competitive Protein Binding ◽  
Intact Rats

SUMMARY Oestradiol-17β in ovarian venous blood and ovarian tissue was assayed by a competitive protein-binding method. Oestradiol was found in similar amounts in the ovarian vein blood of pregnant rats hypophysectomized on Day 12 and killed on Days 16 and 21 and in pregnant rats sham-hypophysectomized on Day 12 and killed on Day 16. The pituitary therefore plays no part in oestrogen production after mid-pregnancy until some time between Day 16 and Day 21, when it gives rise to an increased ovarian venous blood oestradiol content just before parturition, in intact sham-hypophysectomized rats. It is suggested that this increase is associated with the advent of the post-partum ovulation. The corpus luteum and the extraluteal component of the ovary in hypophysectomized rats autopsied on Days 16 and 21 and in sham-hypophysectomized rats autopsied on Day 16, contain similar amounts of oestradiol within each group. The extraluteal component contains about five times more oestradiol than corpora lutea in sham-hypophysectomized intact rats autopsied on Day 21. The ovaries of these animals also show an increased amount of oestradiol over that of the ovaries in the other three groups. It is suggested that secretion of oestradiol after mid-pregnancy in rats involves concurrently both the corpus luteum and the extraluteal component of the ovary.

scholarly journals Mechanisms of hepatic phosphatidylcholine synthesis in adult rat: effects of pregnancy

1994 ◽  
Vol 303 (3) ◽  
pp. 941-947 ◽  
Author(s):  
G C Burdge ◽  
A N Hunt ◽  
A D Postle
Keyword(s):  
Molecular Species ◽  
De Novo ◽  
Essential Fatty Acids ◽  
Maternal Diet ◽  
Liver Microsomes ◽  
Late Pregnancy ◽  
Pregnant Rats ◽  
Adult Rat

Late pregnancy in the rat (gestational ages 16-21 days) was accompanied by a specific increase in hepatic phosphatidylcholine (PC) and phosphatidylethanolamine (PE) molecular species containing C16:0 at the sn-1 position and polyunsaturated essential fatty acids (PUFA), in particular C22:6(n-3), at the sn-2 position. Incorporation of either CDP:[Me-14C]choline or CDP:[1,2-14C]-ethanolamine into hepatic microsomal sn-1 C16:0 PC or PE molecular species in vitro was greater at term than in non-pregnant animals, suggesting modifications to the composition of specific diacylglycerol (DAG) pools destined for synthesis of either PC or PE. Also, incorporation of [Me-14C]choline or [Me-14C]methionine into hepatic PC in vivo over 6 h in term pregnant rats was consistent with decreased phospholipase A1-dependent acyl remodelling of sn-1 C16:0 to sn-1 C18:0 molecular species. There was, however, no evidence to support any change to the specificity of acyl remodelling. The rate of PC synthesis by the de novo pathway in vivo was increased in term liver compared with non-pregnant animals, accompanied by increased choline-phosphotransferase activity in vitro in d21 liver microsomes. The rate of PC synthesis by PE N-methylation did not appear to change during pregnancy. Changes in composition of plasma PC species at term reflected those of newly synthesized hepatic PC. Our data suggest supply of PUFA to the developing fetal rat is the result of specific adaptations to maternal hepatic phospholipid biosynthesis rather than passive transfer from the maternal diet.

scholarly journals Decreased contraction-stimulated glucose transport in isolated epitrochlearis muscles of pregnant rats

2005 ◽  
Vol 98 (3) ◽  
pp. 1021-1027 ◽  
Author(s):  
Raquel Sancho ◽  
Junghoon Kim ◽  
Gregory D. Cartee
Keyword(s):  
Skeletal Muscle ◽  
Glucose Transport ◽  
Contractile Activity ◽  
Late Pregnancy ◽  
Pregnant Rats ◽  
Tension Development ◽  
Glycogen Concentration ◽  
Distal Process ◽  
Relative Decline

Late pregnancy is characterized by insulin resistance for glucose transport in skeletal muscle. The main purpose of this study was to investigate the effect of late pregnancy on contraction-stimulated glucose transport in isolated rat skeletal muscle after in vitro electrical stimulation. Isolated epitrochlearis muscles of 19-day pregnant and aged-matched nonpregnant control rats were studied. One muscle from each rat was stimulated to contract, and the contralateral muscle served as a resting control. Tension developed during contractile activity, 3- O-methylglucose (3-MG) transport rate, and glycogen concentration were determined. Epitrochlearis muscles from other rats were used to measure insulin-stimulated 3-MG transport. There was no detectable difference between the nonpregnant and pregnant groups for contractile performance (peak tension, total tension, or fatigue). Pregnancy was not associated with significant changes in muscle glycogen concentration (resting or after contractile activity) or the contraction-stimulated decrement in glycogen concentration. For muscles from pregnant vs. nonpregnant groups, there was a 22% reduction ( P ≤ 0.05) in contraction-stimulated glucose transport, a 28% decrease ( P ≤ 0.05) in insulin-stimulated glucose transport, and unchanged basal glucose transport. In conclusion, isolated epitrochlearis muscles from pregnant vs. nonpregnant rats had a relative decrement in contraction-stimulated glucose transport that was similar to the relative decline in insulin-stimulated glucose transport. The decrement in contraction-stimulated glucose transport was not attributable to pregnancy-related changes in tension development or glycogen levels. The similar relative decline in insulin- and contraction-stimulated glucose transport raises the possibility that pregnancy impairs a distal process that is common to mechanisms whereby each stimulus activates glucose transport.

Baroreflex control of sympathetic outflow in pregnant rats: effects of captopril

1990 ◽  
Vol 258 (6) ◽  
pp. R1417-R1423 ◽  
Author(s):  
M. E. Crandall ◽  
C. M. Heesch
Keyword(s):  
Base Line ◽  
Operating Pressure ◽  
Sympathetic Outflow ◽  
Arterial Baroreflex ◽  
Nerve Activity ◽  
Pregnant Rats ◽  
Baroreflex Control ◽  
Renal Sympathetic Nerve Activity ◽  
Near Term ◽  
Renal Sympathetic

Arterial baroreflex control of renal sympathetic nerve activity (RSNA) was compared in nonpregnant (NP) and near-term pregnant (P) chloralose-anesthetized rats. Baroreflex curves were obtained by recording reflex changes in RSNA (expressed as a percent of base line) due to increases and decreases in mean arterial pressure (MAP) [intravenous phenylephrine and nitroprusside (NTP)]. The slope, midpoint (EP50), and threshold pressures of the baroreflex curves were compared. Base-line MAP was significantly lower in the pregnant animals (P = 96 +/- 3 vs. NP = 113 +/- 5 mmHg). The baroreflex curves of pregnant animals also had significantly lower threshold (P = 95 +/- 3 vs. NP = 110 +/- 5 mmHg) and midpoint values (P = 105 +/- 4 vs. NP = 119 +/- 5 mmHg). The response to unloading the baroreceptors was attenuated in the pregnant animals as indicated by a decrease in slope of the NTP portion of the baroreflex curve (P = 0.95 +/- 0.17 vs. NP = 1.61 +/- 0.29% nerve activity/mmHg). Responses to blockade of angiotensin-converting enzyme with captopril (2 mg/kg iv) were also examined. There were no differences in EP50 or slope among the control, captopril, and recovery baroreflex curves within either the nonpregnant or pregnant animals. However, after captopril, MAP decreased to a greater extent in the pregnant rats, yet RSNA increased to the same level for the two groups. Thus pregnancy results in a leftward shift of the baroreflex function curve toward a lower operating pressure range. In addition, pregnant rats demonstrated an impaired ability to increase sympathetic outflow above base-line values in response to a hypotensive challenge.

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