Pilot study of once-a-day prophylaxis for youth and young adults with severe haemophilia A

INTRODUCTION

Standard prophylaxis has been shown to be an effective treatment for severe haemophilia A. According to pharmacokinetic principles, daily factor infusions of smaller doses can maintain similar trough factor VIII (FVIII) levels, and perhaps the same protection as standard prophylaxis.

AIM

This multicentre study examined the feasibility of daily prophylaxis for youth and young adults with severe haemophilia A in Montreal and Toronto.

METHODS

Bleeding rates, joint status, quality of life and physical activity were monitored for 14 patients during this study. At baseline, subjects continued their regular treatment regimen and switched to daily prophylaxis after 4 months; nine had begun daily prophylaxis before enrolment. Additional visits occurred at 8 and 12 months which included a physical examination, inhibitor testing, HJHS and FISH assessments, the CHO-KLAT/Haemo-QoL-A and PDPAR. Treatment satisfaction was assessed using the Treatment Satisfaction Questionnaire for Medication ver.II and perceived difficulty questions at the end of study.

RESULTS AND CONCLUSIONS

There were no significant changes in quality of life except for concerns with the demanding daily infusion schedule. The number of bleeds did not statistically differ from the initial 4 months of the study to the last 8 months. Monthly bleeding rates from the year prior to the study and during the intervention phase were not statistically different. It was also found that daily prophylaxis used 24% less FVIII compared to standard prophylaxis. Taking all of this into account, we have found that providing daily prophylaxis is feasible and that it is feasible to prospectively study daily prophylaxis in youth and young adults.

Generic and disease-specific quality of life among youth and young men with Hemophilia in Canada

Background

This study was undertaken to explore the longitudinal patterns of health-related quality of life (HRQoL) among youth and young adults with Hemophilia A (HA) over a 3-year period. This report presents the baseline characteristics of the study cohort.

Methods

Males, 14 to 29 years of age, with predominantly severe HA were recruited from six treatment centres in Canada. Subjects completed a comprehensive survey. HRQoL was measured using: the CHO-KLAT_2.0 (youth), Haemo-QoL-A (young adults) and the SF-36v2 (all).

Results

13 youth (mean age = 15.7, range = 12.9-17.9 years) and 33 young adults (mean age = 23.6; range = 18.4 -28.7 years) with moderate (7 %) and severe (93 %) HA were enrolled. All were on a prophylactic regimen with antihemophilic factor (Helixate FS®) during the study. The youth had minimal joint damage (mean HJHS = 5.2) compared to young adults (mean HJHS = 13.3). The mean HRQoL scores for youth were: 79.2 (SD = 11.9) for the CHO-KLAT, and 53.0 (5.5) and 52.3 (6.8) for the SF-36 Physical Component Summary (PCS) and Mental Component Summary (MCS) scores respectively. The mean HRQoL scores for young adults were: 85.8 (9.5) for the Haemo-Qol-A, and 50.8 (6.4) and 50.9 (8.8) for PCS and MCS respectively. PCS and MCS scores were comparable to published Canadian norms, however significant differences were found for the domains of Physical Functioning and Bodily Pain. The disease-specific HRQoL scores were weakly correlated with the PCS for youth (CHO-KLAT vs. PCS r = 0.28, p = 0.35); and moderately correlated for the MCS (r = 0.39, p = 0.19). Haemo-QoL-A scores for young adults were strongly correlated with the PCS (r = 0.53, p = 0.001); and weakly correlated with the MCS (r = 0.26, p = 0.13). Joint status as assessed by HJHS was correlated with PCS scores. A history of lifelong prophylaxis resulted in better PCS but worse MCS scores.

Conclusion

Despite having hemophilia, the youth in this cohort have minimal joint disease and good HRQoL. The young adults demonstrated more joint disease and slightly worse HRQoL in the domains of physical functioning and pain. The data presented here provide new information to inform the selection of Health Related Quality of Life (HRQoL) instruments for use in future clinical trials involving persons with hemophilia.

Trial registration

ClinicalTrials.gov : NCT01034904. Study funded by CSL Behring Canada.

Electronic supplementary material

The online version of this article (doi:10.1186/s12878-016-0052-x) contains supplementary material, which is available to authorized users.

Effects of moderate-intensity physical exercise on pharmacokinetics of factor VIII and von Willebrand factor in young adults with severe haemophilia A: a pilot study

INTRODUCTION

In persons with severe haemophilia A (pwshA), infused factor VIII (FVIII) half-life can vary according to such determinants as blood group, von Willebrand factor (VWF) level or age; however, FVIII pharmacokinetics (PK) has not been well studied in pwshA during exercise.

AIM

To investigate FVIII PK in pwshA performing moderate-intensity aerobic exercise.

METHODS

Twelve young-adult pwshA with the intron-22 inversion mutation, on relatively low-dose FVIII prophylaxis regimens, and relatively good musculoskeletal status were recruited. Abbreviated PK of FVIII activity and von Willebrand factor antigen (VWF:Ag) level were compared - during rest, and with 60-min exercise (2 × 15 min each of moderate-intensity stationary cycling and treadmill walking). During rest and exercise visits, a baseline blood specimen was drawn, routine prophylaxis FVIII infused; then six blood specimens were taken over the following 24 h.

RESULTS

For all subjects, mean half-life of infused FVIII did not change significantly with exercise vs. at rest (577 ± 190 vs. 614 ± 163 min; P = 0.4131). VWF:Ag rose transiently by 40-50% for 6-8 h with exercise (P < 0.01), particularly in non-O blood group subjects. No musculoskeletal bleeds occurred during the study.

CONCLUSION

Four × 15 min of moderate-intensity aerobic exercise increased VWF:Ag levels for 6-8 h, and showed no evidence of accelerated FVIII clearance or of musculoskeletal bleeding in these young-adult pwshA with relatively good musculoskeletal status, on relatively low-dose FVIII prophylaxis regimens. However, O blood group impact would merit larger studies, with longer durations of similar or more vigorous exercise intensities.

Patterns of tertiary prophylaxis in Canadian adults with severe and moderately severe haemophilia B

From a young age patients with severe and moderately severe FIX deficiency (haemophilia B) can experience spontaneous or traumatic bleeding and joint destruction may result. The use of coagulation factor IX concentrate to prevent anticipated bleeding, as primary or secondary prophylaxis, has become a common and recommended practice in children. The current practice of using tertiary prophylaxis, in the presence of established joint arthropathy, in adults with haemophilia B is not well characterized. This observational study was conducted to gain a better understanding of the recent Canadian experience with tertiary prophylaxis in adults with severe and moderately severe haemophilia B. Data were collected from all eligible adult (≥ 18 years of age) males with baseline FIX:C ≤ 2% from seven Canadian Hemophilia Treatment centres over a 2-year observation period from 2009 to 2011. Thirty-four per cent of the 67 subjects with moderately severe haemophilia B were exposed to prophylaxis with the majority as continuous prophylaxis (≥45 weeks year(-1) ). The severe subgroup (FIX:C < 1%) demonstrated a 52% exposure rate. None had primary prophylaxis exposure in childhood. Eighty-one per cent used once or twice weekly infusion regimens and reported a median annual bleeding rate of five bleeds per year versus four bleeds per year for those using on-demand treatment. Annual median factor utilization for all subjects using prophylaxis was 196,283 U year(-1) compared to 46,361 U year(-1) for on demand. Approximately 50% of adults with severe haemophilia B are using continuous tertiary prophylaxis in Canada, a practice likely to increase which warrants further study.

Bleeding disorders, menorrhagia and iron deficiency: impacts on health-related quality of life

von Willebrand disease (VWD) is a bleeding disorder that occurs in up to 1% of the general population. The great majority of females with VWD experience menorrhagia. The morbidity burden in females with VWD may relate to iron deficiency resulting from menorrhagia. To explore relationships between bleeding disorders, menorrhagia, iron deficiency and the outcomes of health-related quality of life (HRQL) and educational attainment. All subjects with VWD, and females with other bleeding disorders, in the Canadian national registry who were more than 12 years of age were eligible for survey. Survey measures included the HEALTH UTILITIES INDEX(®); abridged Clinical History Assessment Tool; socio-demographic questions and serum ferritin. Statistical analyses included testing differences among groups of means using analysis of variance and of proportions using chi-squared test. Significant size differences in mean HRQL scores were detected between VWD females and both females with other bleeding disorders [diff = (-0.08); P = 0.017] and VWD males [diff = (-0.07); P = 0.039]. Mean HRQL scores differed between females with and without menorrhagia (P < 0.001). Mean HRQL scores were not significantly different between females with and without iron deficiency. Educational attainment was not associated with disease group, menorrhagia status or iron status. Females with VWD have a greater morbidity burden than females in the general population, females with other bleeding disorders and males with VWD. Menorrhagia is associated with low HRQL scores in females with bleeding disorders, including VWD. Further investigation should assess how menorrhagia impacts HRQL in females with bleeding disorders.

Regulation of the sodium pump during cardiomyocyte adaptation to pregnancy

Regulation of the sodium pump during normal pregnancy and its effect on the function of cardiomyocytes is poorly understood. Our objective was to evaluate the possible implication of the Na(+)-K(+)-ATPase, the sodium pump which controls cellular ionic and metabolic homeostasis, in the adaptations of cardiomyocytes to normal pregnancy. We have used Western blots and patch-clamp measurements to identify changes in the sodium pump proteins. Confocal microscopy was applied to estimate intracellular sodium concentration. Time-resolved spectroscopy was employed to measure mitochondrial NAD(P)H fluorescence and estimate oxidative metabolic state. Optical microscopy was adopted to study the contractility responses of cardiomyocytes. Cells from non-pregnant and pregnant rats (1 day prior parturition) were studied. Our results showed lower protein expression of the α1 Na(+)-K(+)-ATPase isoform in cardiomyocytes in pregnant rats, decreased sodium pump membrane current and elevated steady-state sodium concentration. In addition, ouabain, the inhibitor of the sodium pump capable of increasing cardiomyocyte contractility in non-pregnant rats in a concentration-dependent manner, failed to affect cell contractions in pregnant rats. We also noted modified responsiveness of the mitochondrial metabolic state to ouabain in cardiac cells. The gathered data confirmed that in pregnant rats, the sodium pump protein content and transmembrane flux are decreased, while the sensitivity of cardiomyocyte contractility and the sensitivity of mitochondrial metabolic redox state to ouabain are modified, pointing to regulation of the Na(+)-K(+)-ATPase during cardiac cell adaptations to normal pregnancy.

Mineralocorticoids participate in the reduced vascular reactivity of pregnant rats

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(-1)·day(-1)) 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, high-conductance 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.

Cross-cultural validation of the CHO-KLAT and HAEMO-QoL-A in Canadian French

Multi-site studies are necessary in the field of haemophilia to ensure adequate sample sizes. Quality of life (QoL) instruments need to be harmonized across languages and cultures to facilitate their inclusion. The purpose of this study was to adapt the Canadian Haemophilia Outcomes - Kids Life Assessment Tool (CHO-KLAT(©)) and HAEMO-QoL-A(©) to French for Canada. The CHO-KLAT and the HAEMO-QoL-A are haemophilia-specific measures of QoL for boys and men respectively. Both measures originated in English, were translated into Canadian French by clinicians with expertise in haemophilia care, back-translated by expert translators and harmonized by a multi-disciplinary team. The harmonized versions were evaluated through a cognitive debriefing process with 6 boys with haemophilia, their parents and 10 men with haemophilia. The final versions were validated in a sample of 19 boys with haemophilia, 19 parents, and 22 men with haemophilia along with a generic QoL scale: the PedsQL for children; and the SF-36 for adults. The translation and cognitive debriefing processes resulted in a preliminary version that maintained the intent of the original questions. The validation study estimated the mean score for the child-reported CHO-KLAT at 71.9 (SD 10.4), and the adult-reported HAEMO-QoL-A at 79.1 (SD 21.3). The CHO-KLAT correlated 0.64 with the PedsQL and the HAEMO-QoL-A correlated 0.78 with the SF-36 physical component summary score. The French-Canadian version of the CHO-KLAT and HAEMO-QoL-A are valid. These measures are available for use in multi-site haemophilia trials and clinical practices to capture QoL data from French Canadians.

Low prevalence of inhibitor antibodies in the Canadian haemophilia population

Annual reporting of inhibitors to factors (FVIII) and IX (FIX) to the Canadian Haemophilia Registry has suggested a lower prevalence than that published in the literature. We performed a prospective study to determine the prevalence of patients with inhibitors directed against either FVIII or FIX. Patients with inhibitors were classified as: (i) inhibitor test positive; (ii) inhibitor test negative but on immune tolerance induction (ITI); (iii) inhibitor test negative but bypass treatment recommended; or (iv) inhibitor resolved. One year later, the cohort was re-classified. The prevalence of inhibitors on 1 May, 2007 was 3.3% for haemophilia A, 0.6% for haemophilia B and 8.9% and 2.1% for severe haemophilia A and B. One year later 17 individuals gained and 11 individuals lost inhibitor status (10 of these with ITI). This study suggests that the prevalence of inhibitors in our population is lower than that was previously published. We hypothesize that this is primarily due to the increased use of ITI, but other factors may be the unselected nature of the cohort and the restriction of the study to one date thereby conforming as close as practical to the definition of prevalence rather than incidence. The classification system used in this study was easy for clinics to apply and was important in defining the population with inhibitors.

Placental oxidative stress in a rat model of preeclampsia

The onset of preeclampsia is associated with increased maternal insult that could affect placental function. By increasing sodium intake (0.9% or 1.8% NaCl in drinking water) during the last week of gestation in the rat, we developed an animal model that shows many characteristics of preeclampsia such as increased blood pressure, decreased circulatory volume and diminished activity of the renin-angiotensin-aldosterone system. The aim of the present study was to determine in this model whether maternal perturbations in pregnancy lead to placental oxidative stress. Sprague-Dawley pregnant rats receiving salted-water were compared to not-supplemented pregnant rats. Markers of oxidative stress, ensuing cell death, and changes in the production of vasoactive substances (prostanoids: thromboxane, TxB(2); and prostacyclin, PGF(1alpha)) and the pro-inflammatory cytokine tumour necrosis factor-alpha (TNF-alpha) were measured in the placenta. In tissue from pregnant rats on 1.8% NaCl supplement, 8-iso-PGF(2alpha) levels, TxB(2)/6-keto-PGF(1alpha) ratios, total TNF-alpha RNA expression, as well as the apoptotic index (Bax/Bcl-2 ratio) and endothelial nitric oxide synthase protein expression increase while total glutathione content decreases. These findings demonstrate that maternal insult during gestation induced an imbalance in the oxidative environment in the placenta favouring oxidation. This was accompanied by an increased synthesis of vasoconstrictive substances and TNF-alpha by the placenta as well as the increased rate of placental cell apoptosis.

Can activated recombinant factor VII be used to postpone the exposure of infants to factor VIII until after 2 years of age?

Two retrospective studies have suggested that exposure to factor VIII (FVIII) in early infancy is associated with an increased risk of FVIII inhibitor development. We prospectively studied 11 infants who needed replacement therapy for bleeding episodes before the age of 2 years. They received activated recombinant factor VII (rFVIIa) concentrate on demand, with the intention of postponing their first exposure to FVIII after 2 years of age. Thirty-three bleeding episodes were treated with 154 doses of rFVIIa with no evidence of adverse effect. Bleeding was controlled in 27 of 33 episodes. Mouth bleeds were most difficult to treat. The use of rFVIIa allowed postponement of the use of FVIII for a mean of 5.5 months (median 4, range 0-12) but in only three of 11 children could be the first exposure to factor postponed after the age of 2 years. With this modest effect of rFVIIa in postponing the first exposure to FVIII, more convincing evidence for the benefit of such a postponement will have to be demonstrated before rFVIIa could be recommended for this indication.

Vascular responses to alpha-adrenergic stimulation and depolarization are enhanced in insulin-resistant and diabetic Psammomys obesus

Since vascular complications often accompany diabetes, we examined the influence of the endothelial lining on vascular reactivity in Psammomys obesus, a desert gerbil that acquires insulin resistance and diabetes when exposed to a laboratory diet. Vasoconstriction to phenylephrine and depolarizing KCl, as well as carbachol endothelium-dependent relaxation, were assessed in rings of thoracic aortae obtained from three groups: (i) group A, normoglycemic-normoinsulinemic; (ii) group B, normoglycemic-hyperinsulinemic, and (iii) group C, hyperglycemic-hyperinsulinemic animals. As expected, marked hypertriglyceridemia and hypercholesterolemia characterized groups B and C, which developed enhanced contractile responsiveness to phenylephrine and KCl compared with controls (group A). Furthermore, both experimental groups displayed a significant decrease in endothelium-dependent relaxation to carbachol. Altered lipid profiles are considered to play some role in the observed modification of aortic reactivity. Overall, our data indicate that vascular contractile responsiveness is enhanced early in the development of insulin resistance and diabetes in the female P. obesus.

Optimization of storage conditions for diluted working solutions of porcine factor VIII and performance of the Bethesda assay for the determination of antiporcine FVIII inhibitor titres

The use of porcine factor VIII (FVIII) (Hyate:C, Ipsen) has proven to be very successful in treating patients with FVIII inhibitors. The best way to predict the usefulness of porcine FVIII therapy, and/or to estimate the appropriate treatment dose in a given patient, is to measure the patient inhibitor titre against porcine FVIII with the Bethesda assay, using porcine FVIII as the source of FVIII in the assay. The goals of the present study were to (1) find the optimal storage temperature, diluent and concentration for a working solution of porcine FVIII to be used as the source of FVIII for the porcine Bethesda assay, (2) assess the reliability of the labelled FVIII units in the preparation of such working solutions of porcine FVIII and (3) compare the inhibitor titres determined by the Bethesda assay using both porcine and human standard reference curves for measuring residual FVIII. The results of the present study demonstrate that a ready-to-use working solution of 1 U mL(-1) of Hyate:C diluted in human FVIII deficient plasma, either containing or deficient in von Willebrand factor antigen, is stable for up to 12 months, at -20 degrees C. The preparation of the 1 U mL(-1) working solution could be reliably calculated based on the units indicated on the vial label. Finally, using the human standard curve yields similar results to using the porcine standard curve for measuring any titre of allo- or auto-antibody against FVIII in the Bethesda assay, using Hyate:C as the source of FVIII. These findings are of practical value when performing a porcine FVIII-based Bethesda assay.

Blockade of angiotensin receptor subtypes in arcuate uterine artery of pregnant and postpartum rats

During pregnancy, uterine circulation undergoes hypertrophy and hyperplasia. We investigated the effects of angiotensin (Ang) II receptor subtype (AT(1)/AT(2)) blockade on increased responses to the peptide during reversible remodeling of the uterine vasculature in pregnant and postpartum rats. Uterine arcuate arteries were set up in wire myographs for microvessel and submitted to a tension equivalent to 50 mm Hg transmural pressure. Cumulative concentration-response curves to Ang II were measured in the absence and presence of losartan on the same vascular segment. A similar protocol was repeated in the presence of PD 123,319, an AT(2) receptor blocker, again in the absence and presence of losartan. Responses to Ang II on the arcuate artery increased markedly during pregnancy and returned to the prepregnant level within 12 days postpartum. Losartan (10(-7) mol/L) produced a parallel right shift of the concentration-response curve to Ang II in all groups of tissues, but potency of the AT(1) receptor blocker was reduced at the end of pregnancy and in the early postpartum period. PD 123,319 (10(-7) mol/L) significantly increased maximum response to Ang II in arterial segments of the nonpregnant, term-pregnant, and 5 days postpartum rats. AT(1) receptor expression was decreased in arcuate arteries of term-pregnant rats. These results show that contractile responses to Ang II on the uterine arcuate artery of the rat are mediated by the AT(1) receptor and that blockade of AT(2) receptors potentiated responses to the peptide. They also indicate that, in uterine vessels, AT(2) receptor stimulation interferes with Ang II responses, but this effect is decreased in uterine arcuate arteries in the peripartum period.

Functional alteration of dihydropyridine-sensitive Ca(2+) channels in the adrenal glomerulosa of pregnant rats

Our previous work on aldosterone secretion suggested that dihydropyridine-sensitive calcium channels, one type of voltage-dependent calcium channels (VDCC), are functionally impaired in adrenal capsule preparations from the pregnant rat. The aim of this study was to determine whether, during pregnancy, the density and/or activity of these channels is altered in the adrenal zona glomerulosa. These VDCC measured with [(3)H]nitrendipine binding were not different between membrane preparations of nonpregnant and pregnant rats. Western blots were performed using two different antibodies, a polyclonal (PcAb) directed against the alpha(1)-subunit of VDCC and a monoclonal (McAb) that recognizes an intracellular domain of that protein. McAb immunoreactivity showed a significant decrease in preparations from pregnant rats, whereas no difference was observed with PcAb. VDCC activity was estimated by (45)Ca(2+) uptake in isolated adrenal cortex and by intracellular calcium concentration ([Ca(2+)](i)) in adrenal glomerulosa cells with the Ca(2+) probe fura PE3. These measurements revealed that KCl stimulation produced greater Ca(2+) influx in nonpregnant than in pregnant rats. Nifedipine (a blocker of VDCC) inhibited this stimulation only in nonpregnant rats, whereas BAY K 8644 (an activator of VDCC) increased Ca(2+) influx in pregnant rats only. These data suggest that, during pregnancy, the altered regulation of calcium homeostasis in adrenal glomerulosa is linked to a conformational alteration of VDCC.

Effects of potassium channel modulators on myotropic responses of aortic rings of pregnant rats

The contribution of potassium channels [ATP-sensitive potassium (K(ATP)) and high-conductance calcium-activated potassium (BK(Ca)) channels] in the resistance of aortic rings of term pregnant rats to phenylephrine (Phe), arginine vasopressin (AVP), and KCl was investigated. Concentration-response curves to tetraethylammonium (TEA), a nonselective K(+) channel inhibitor, were obtained in the absence or presence of KCl. TEA induced by itself concentration-dependent responses only in aortic rings of nonpregnant rats. These responses to TEA could be modulated in both groups of rings by preincubation with different concentrations of KCl. Concentration-response curves to Phe, AVP, and KCl were obtained in the absence or presence of cromakalim or NS-1619 (K(ATP) and BK(Ca) openers, respectively) and glibenclamide or iberiotoxin (K(ATP) and BK(Ca) inhibitors, respectively). Cromakalim significantly inhibited the responses to the three agonists in a concentration-dependent manner in both groups of rats. Alternatively, in the pregnant group of rats, glibenclamide increased the sensitivity to all three agonists. NS-1619 also inhibited the response to all agonists. With AVP and KCl, its effect was greater in aortic rings of pregnant than nonpregnant rats. Finally, iberiotoxin increased the sensitivity to all three agents. This effect was more important in aortic rings of nonpregnant rats and was accompanied by an increase of the maximal response to Phe and AVP. These results suggest that potassium channels are implicated in the control of basal membrane potential and in the blunted responses to these agents during pregnancy.

Modulation of calcium mobilization in aortic rings of pregnant rats: Contribution of extracellular calcium and of voltage-operated calcium channels

Pregnancy is associated with decreased vascular responsiveness to vasopressor stimuli. We have tested the involvement of Ca2+ mobilization in myotropic responses of aortic rings obtained from pregnant and virgin rats. Contractions of the rings to phenylephrine, in the absence of calcium in the bathing medium, were lower in tissues from virgin than from pregnant rats. Concentration-response curves to CaCl2 that were measured after stimulation by phenylephrine in the absence of Ca2+ were shifted to higher levels of contraction. This was not observed when KCl was used to prestimulate the aorta. D-600, a phenylalkylamine calcium channel blocker, similarly inhibited these responses to CaCl2 in tissues from both pregnant and virgin animals. D-600 exerted a concentration-dependent inhibition of responses to phenylephrine and KCl. However, the calcium antagonist was less effective in aortic rings of pregnant than of virgin rats. Basal 45Ca2+ uptake was lower in aortic rings from pregnant than from virgin rats, and Bay K 8644 was unable to reverse this difference. The time course of basal and stimulated (KCl) 45Ca2+ influx was lower in aorta of pregnant rats at all times studied. Moreover, when the intracellular calcium pools were emptied with phenylephrine, the refilling of these pools was delayed in aortic rings of pregnant rats. These results indicate an altered extracellular calcium mobilization of aortic rings from pregnant rats. These changes may be due to a functional alteration of the voltage-operated calcium channels during pregnancy.

Induction of intrauterine growth restriction with a low-sodium diet fed to pregnant rats

OBJECTIVE

A low-sodium diet fed to female rats before mating through parturition leads to pups of lower weight. We characterized the effect of low dietary sodium during the last week of gestation (after fetal organogenesis) on fetal and maternal homeostasis.

STUDY DESIGN

Pregnant Sprague-Dawley rats were randomly assigned to a control group or to a group fed a low-sodium diet from gestational days 15 through 22. Systolic blood pressures were measured throughout pregnancy. On day 22 plasma volume was measured and blood samples were taken for electrolyte and hormonal measurements. Fetal and placental weights were also determined.

RESULTS

Plasma renin activity and aldosterone level were significantly higher in the experimental group than in the control group. Plasma volume was significantly lower in pregnant rats receiving a low-sodium than in those receiving a control diet. Rats receiving a low-sodium diet had pups of lower weight and length (4.45 +/- 0.22 g, 3.90 +/- 0.06 cm) than pups of the control group (5.21 +/- 0.12 g, 4.10 +/- 0.02 cm). Pups born to mothers with low-sodium diets recuperated from intrauterine growth restriction by 14 days after birth.

CONCLUSION

These data indicate that a low-sodium diet given to pregnant rats for the last 7 days of gestation leads to reduced plasma volume expansion and fetal growth restriction. This could prove to be a simple animal model for studying the relationship between maternal plasma volume and fetal growth.

Reactivities to serotonin and histamine in umbilical and placental vessels during the third trimester after normotensive pregnancies and pregnancies complicated by preeclampsia

OBJECTIVE

The aim of the study was to evaluate responses of umbilical and placental arteries and veins to serotonin and histamine after normotensive pregnancies and pregnancies complicated by preeclampsia.

STUDY DESIGN

Each pair of placentas from a normotensive woman and a woman with preeclampsia was matched for gestational age. Rings of these vessels were prepared and mounted in tissue baths under their respective optimal passive tension. Cumulative concentration-response curves to serotonin and histamine were measured.

RESULTS

Responses to serotonin were decreased in umbilical vessels from the preeclampsia group with respect to the normotensive group. This is reflected by reduced maximum responses and sensitivity (negative logarithm of the 50% effective concentration) to serotonin. Maximum response to serotonin was significantly decreased in placental vein rings from the preeclampsia group. We recorded a decreased maximal response to histamine in placental vein rings from pregnancies complicated by preeclampsia with respect to those from normal pregnancies. Among normotensive women there was a significant positive linear relationship between neonatal weight and sensitivity to serotonin in umbilical and placental veins. This relationship was totally absent in preeclampsia. Sensitivity to histamine was linearly related to neonatal weight in umbilical vessels of the pooled results of both experimental groups.

CONCLUSION

The vasoconstrictive effects of serotonin, but not those of histamine, are decreased in umbilical and placental vessels after preeclampsia. Sensitivities to serotonin and histamine change in umbilicoplacental vessels during the third trimester. Altered reactivity to serotonin may play a significant role in the reduction of umbilicoplacental blood flow in preeclampsia.

In vivo regulation of enzymes controlling aldosterone synthesis in pregnant rats

There are two main regulatory sites of aldosterone biosynthesis, the early rate-limiting step by the P450scc and the final steps by the P450aldo. We have already demonstrated that, during gestation, activity and mRNA levels of P450aldo are increased. It has been shown that changes in sodium and potassium in the diet modulate the expression of P450aldo in adrenal zona glomerulosa (ZG). In the present study, we compared the effects of low-sodium (Na+) and high-potassium (K+) diet on the expression of enzymes controlling aldosterone synthesis during gestation. Pregnant and nonpregnant rats were randomly assigned to control group or to group receiving low Na+ or high K+ diet during the last week of pregnancy. By the end of the treatment, the two diets induced increases of plasma aldosterone and P450aldo mRNA levels in nonpregnant and pregnant rats. However, plasma renin activity and P450scc mRNA levels were only in the pregnant group fed the low Na+ diet. High K+ diet had no effect on these parameters. We, thus, suggest that the renin-angiotensin system and the enzymes implicated in aldosterone synthesis are differently regulated during gestation.

Tyrosine kinase and MAPK inhibition of TNF-alpha- and EGF-stimulated IEC-6 cell growth

The role of TNF-alpha in modulating intestinal crypt cell growth was examined, in comparison with EGF. Both significantly increased IEC-6 cell proliferation. Neither EGF nor TNF-alpha overcame the inhibitory effect on growth exerted by the tyrosine kinase inhibitor genistein. Immunoblots with phosphotyrosine antibodies showed increased tyrosine phosphorylation of IEC-6 cell proteins in response to EGF and TNF-alpha stimulation. TNF-alpha increased ERK1 and ERK2 MAPK phosphorylation. A MAPK assay confirmed the increased activity upon TNF-alpha stimulation. Selective inhibition of MAPK activation by PD98059 resulted in a dose dependent inhibition of TNF-alpha or EGF-induced IEC-6 cell growth. These findings suggest a role for TNF-alpha in the regulation of intestinal epithelial cell growth and that the mitogenic effect of TNF-alpha requires protein tyrosine phosphorylation and MAPK activation.