Different effects of oral and transdermal hormonal replacement on prostacyclin and thromboxane A2

OBJECTIVE

To elucidate the mechanism of cardiovascular protection of hormone replacement therapy (HRT) by comparing the effect of oral and transdermal HRTs on the production of antiaggregatory, vasodilatory prostacyclin, and its endogenous antagonist, thromboxane A2.

METHODS

Oral estradiol (2.0 mg/d) plus norethisterone acetate (1.0 mg/d) (n = 13) or transdermal estradiol (50 micrograms/d) plus medroxyprogesterone acetate (10 mg/d) as 12-day courses at 4-week intervals (n = 13) were given to postmenopausal women. Urinary excretion of the metabolites of prostacyclin, ie, 6-ketoprostaglandinF1 alpha and 2,3-dinor-6-ketoprostaglandinF1 alpha, as well as those of thromboxane A2, ie, thromboxane B2 and 2,3-dinor-thromboxane B2, were measured by radioimmunoassays, after purification by extraction and high performance liquid chromatography, before and during the sixth and the 12th treatment cycles.

RESULTS

Oral HRT stimulated excretion of thromboxane B2 from 3.4 +/- 0.7 ng/mmol creatinine to 4.5 +/- 1.5 (mean +/- standard deviation, P < .05) and that of 2,3-dinor-thromboxane B2 from 16.6 +/- 8.0 ng/mmol creatinine to 26.2 +/- 10.7 (P < .01), and thus led to the dominance of thromboxane A2. No changes in prostanoids occurred during transdermal HRT.

CONCLUSIONS

The effects of various HRTs on prostanoids may significantly differ.

Long-chain 3-hydroxyacyl-coenzyme A dehydrogenase deficiency with the G1528C mutation: clinical presentation of thirteen patients

Long-chain 3-hydroxyacyl-coenzyme A (CoA) dehydrogenase is one of three enzyme activities of the mitochondrial trifunctional protein. We report the clinical findings of 13 patients with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency. At presentation the patients had had hypoglycemia, cardiomyopathy, muscle hypotonia, and hepatomegaly during the first 2 years of life. Seven patients had recurrent metabolic crises, and six patients had a steadily progressive course. Two patients had cholestatic liver disease, which is uncommon in beta-oxidation defects. One patient had peripheral neuropathy, and six patients had retinopathy with focal pigmentary aggregations or retinal hypopigmentation. All patients were homozygous for the common mutation G1528C. However, the enoyl-CoA hydratase and 3-ketoacyl-CoA thiolase activities of the mitochondrial trifunctional protein were variably decreased in skin fibroblasts. Dicarboxylic aciduria was detected in 9 of 10 patients, and most patients had lactic acidosis, increased serum creatine kinase activities, and low serum carnitine concentration. Neuroradiologically there was bilateral periventricular or focal cortical lesions in three patients, and brain atrophy in one. Only one patient, who has had dietary treatment for 9 years, is alive at the age of 14 years; all others died before they were 2 years of age. Recognition of the clinical features of long-chain 3-hydroxyacyl-CoA deficiency is important for the early institution of dietary management, which may alter the otherwise invariably poor prognosis.

Nitric oxide as a challenge for the clinical chemistry laboratory

Nitric oxide (NO) is an important intra- and intercellular mediator. Although NO can be measured using many different chemical methods, the compound is challenging for a clinical chemistry laboratory, since its half-life in vivo in humans is only a few seconds. Most of the NO is oxidized to nitrite/nitrate, and the concentrations of these anions have been used as quantitative indices of NO production. The simplest and most widely used technique is spectrophotometric measurement of nitrite using the Griess reaction. Nitrate, the main metabolite of NO in blood and urine, must be reduced to nitrite before the colour reaction. Other methods used for measuring nitrite/nitrate in human blood or urine include high-performance liquid chromatography, gas chromatography-mass spectrometry, chemiluminescence, enzymatic assay with nitrate reductase and electron paramagnetic resonance. The reported mean concentrations of nitrite in the blood of healthy adults have varied from non-existent to 4.2 mumol l-1, and those of nitrate from 19.7 to 44 mumol l-1. The technical measurement of nitrite/nitrate is obviously reliable, but there are problematic preanalytical factors. Normal daily food contains more nitrate than that formed from NO, and thus diet-derived nitrate may contribute considerably to the concentration in blood. The problem may to some extent be solved with dietary restrictions, but it is questionable whether the confounding effect of diet-derived nitrate can be totally avoided. Therefore, better methods for measuring the production of NO in vivo would be very welcome.

Effect of physiological concentrations of estradiol on PGI2 and NO in endothelial cells

OBJECTIVES

To elucidate the mechanisms by which estrogens protect against occlusive vascular disorders, we studied the effect of 17 beta-estradiol on the production of prostacyclin (PGI2) and nitric oxide (NO) in primary cultures of human umbilical vein endothelial cells (HUVECs).

METHODS

To study the effect of 17 beta-estradiol on PGI2 production, HUVECs were incubated in the absence and presence of 17 beta-estradiol (0.01-10 nmol/l) encapsulated within beta-cyclodextrin for 12 h in serum-free medium. To study the effect of 17 beta-estradiol (100 nmol/l) on maximal calcium-dependent NO production, we used different approaches. First, HUVECs were incubated with 2 mumol/l calcium ionophore A23187 with or without 17 beta-estradiol (100 nmol/l) for 24 h in serum-free medium. Second, HUVECs were preincubated with or without 17 beta-estradiol (100 nmol/l) for 12 h in medium supplemented with 2% fetal calf serum, and thereafter incubated in serum-free medium with 2 mumol/l of A23187 and with 100 nmol/l of 17 beta-estradiol (cells which contained 17 beta-estradiol during the preincubation period as well as cells which did not) or without it (only cells which did not contain 17 beta-estradiol during the preincubation period) for 6 h or 24 h.

RESULTS

17 beta-Estradiol (0.1 nmol/l) increased the concentration of 6-keto-prostaglandin F1 alpha, a stable metabolite of PGI2 in the incubation medium, by 16%, and no further increase occurred with higher 17 beta-estradiol concentrations. The stimulation was prevented by tamoxifen. 17 beta-Estradiol did not affect NO production in any of our experiments measured as accumulation of nitrate and nitrite in the experimental medium.

CONCLUSIONS

The stimulatory effect on PGI2 production of physiological concentrations of 17 beta-estradiol, shown now for the first time, may provide one explanation for the ability of 17 beta-estradiol to protect against occlusive vascular disorders.

Hormone replacement therapy modifies the capacity of plasma and serum to regulate prostacyclin and endothelin-1 production in human vascular endothelial cells

OBJECTIVE

To determine if hormone replacement therapy (HRT) modifies the ability of plasma or serum to regulate the synthesis of vasodilatory prostacyclin and that of vasoconstrictive endothelin-1 by cultured human umbilical vein endothelial cells.

DESIGN

Plasma and serum collected before and during the sixth treatment cycle of HRT from 13 healthy postmenopausal women were added to cultured endothelial cells.

SETTING

Helsinki University Central Hospital, Department of Obstetrics and Gynecology, Helsinki, Finland.

PATIENTS

Thirteen postmenopausal women (> or = 1 year since their last menstruation, FSH level > 40 mIU/mL [conversion factor to SI unit, 1.00], clear vasomotor symptoms) that suffered from incapacitating menopausal symptoms necessitating the initiation of HRT were studied.

INTERVENTIONS

A combined regimen consisting of 2 mg oral E2 for 12 days followed by 2.0 mg oral E2 + 1.0 mg norethisterone acetate for 10 days and 1.0 mg E2 for 6 days.

MAIN OUTCOME MEASURES

The releases of prostacyclin, as assessed by its metabolite 6-keto-prostaglandin F1 alpha, and that of endothelin-1 by cultured human umbilical vein endothelial cells in the presence of 10% plasma or 10% serum collected from the study subjects.

RESULTS

Hormone replacement therapy enhanced the ability of plasma to stimulate prostacyclin production by 21% +/- 6% (mean +/- SEM) during the E2 + norethisterone acetate phase and tended to do so also during the E2-only phase (11% +/- 10%) but caused no change in endothelin-1 release. In contrast, HRT decreased the ability of serum to stimulate prostacyclin production by 12% +/- 5% during the E2-only phase and increased that of endothelin-1 by 8% +/- 4% during the E2 + norethisterone acetate phase.

CONCLUSION

Because plasma flushes endothelial cells in vivo, our data on the HRT-induced stimulation of the capacity of plasma to enhance the production of vasoprotective prostacyclin without a concomitant change in endothelin-1 release in cultured human umbilical vein endothelial cells may provide one new explanation for the cardiovascular protection of HRT.

Hirudin stimulates prostacyclin but not endothelin-1 production in cultured human vascular endothelial cells

To study the effect of hirudin on endothelial cell prostacyclin (PGI2) and endothelin-1 (ET-1) production, we cultured human umbilical vein endothelial cells (HUVECs), stimulated them with 0.00001-10 kU/l of hirudin for 12-24 hours, and measured by radioimmunoassays the concentrations of 6-ketoprostaglandinF1 alfa (6-keto, a metabolite of PGI2) and ET-1 in the incubation medium. In incubation medium containing 10% serum hirudin stimulated PGI2-production dose-dependently. The lowest stimulatory hirudin concentration was 0.001 kU/l, which increased the concentration of 6-keto by 10.8 +/- 4.4% (mean +/- S.E) (p < 0.01). The greatest stimulation rate (28.6 +/- 6.2%, p < 0.001) was obtained with the highest hirudin concentration (10 kU/l), when the culture medium contained 10% human serum. The PGI2-stimulating activity was exaggerated in the absence of serum, when 1 kU/l of hirudin increased PGI2-production by 59.7 +/- 6.2% (p < 0.001, n = 14). Stimulation of PGI2 appeared after 12 hour incubation. Hirudin had no effect on the conversion of exogenous arachidonic acid to 6-keto or on the production of ET-1. We thus conclude that hirudin stimulates PGI2-production through de novo protein synthesis. Stimulation of PGI2-production by hirudin may contribute to its antithrombotic activity, since PGI2 favours vasodilatation and attenuates platelet aggregation.

The calcium-dependent nitric oxide production of human vascular endothelial cells in preeclampsia

OBJECTIVE

Nitric oxide is an important vasodilator, and in this study we studied whether the calcium-dependent nitric oxide production capacity of human umbilical vein endothelial cells was affected by preeclampsia.

STUDY DESIGN

Human umbilical vein endothelial cells were isolated from 11 preeclamptic and 10 normotensive pregnancies. The maximal calcium ionophore A23187-stimulated nitric oxide production capacity was measured as accumulation of nitrate and nitrite into the culture medium, and it was related to the number of viable endothelial cells by measurement of their mitochondrial dehydrogenase activity.

RESULTS

The cell number-related nitric oxide production capacity was similar in preeclamptic and normotensive pregnancies. The total nitric oxide production of cells from preeclamptic pregnancies was significantly lower (p <0.001). This difference, however, was mainly caused by larger amount of viable endothelial cells recovered from normotensive pregnancies.

CONCLUSION

The maximal calcium-dependent nitric oxide production capacity of individual human umbilical vein endothelial cells is not affected by preeclampsia.

High bone density in hyperandrogenic women: effect of gonadotropin-releasing hormone agonist alone or in conjunction with estrogen-progestin replacement

We studied 20 hirsute patients with high levels of serum testosterone (T), calculated free T, androstenedione, and dehydroepiandrosterone sulfate and 19 age-matched nonhirsute normoandrogenic control women. The bone mineral density (BMD) in the lumbar spine, femoral neck, and trochanter major region in hirsute patients was higher than that in the controls. BMD in the lumbar spine and proximal femur correlated positively with the body mass index and with serum T and free T in hyperandrogenic women and the whole study group, but not with serum androstenedione or dehydroepiandrosterone sulfate levels. The hirsute women were treated with a GnRH agonist (goserelin, 3.6-mg implant) for 9 months. After the first 3 months of treatment, half of the patients were randomized to receive estrogen-progestin replacement therapy (HRT), and the other half served as controls. After the first 3 months of trial, BMD was unaffected, and the urinary output of collagen pyridinoline, deoxypyridinoline cross-links, and hydroxyproline (all markers of bone resorption) were increased, but serum markers, the carboxy-terminal telopeptide of type I collagen (marker of bone resorption) and that of bone-specific alkaline phosphatase (marker of bone formation) did not change. After 9 months of goserelin treatment, the lumbar spine had lost 5.4% of its BMD (P < 0.01), but regained bone density 6 months after cessation of treatment. Addition of HRT protected the spine and trochanter major against bone loss. The changes in serum telopeptide and urinary output of pyridinoline and deoxypyridinoline after 3 months of treatment (from prestudy levels) correlated with the decrease in BMD in the femoral neck at 9 months. In conclusion, our data show that patients with ovarian androgen excess 1) have high BMD, 2) lose bone during 9 months of treatment with GnRH agonist, 3) show a decrease in bone density preceded by biochemical alterations in bone metabolism at least 6 months earlier, and 4) can have their bone loss prevented by add-back HRT.

Postmenopausal hormonal replacement decreases plasma levels of endothelin-1

Hormone replacement therapy (HRT) protects against cardiovascular disorders, but the mechanisms of this action are poorly understood. We assessed the plasma levels of vasoconstrictive endothelin-1 (ET-1) in 26 healthy postmenopausal women before and during HRT. The women were randomized to receive either continuous transdermal (estradiol 50 ug/24 hrs) complemented with periodic 12 days' courses with medroxyprogesterone (10.0 mg/day)(n = 13) or continuous oral estradiol (2.0 mg/day) and continuous norethisterone acetate (1.0 mg/day)(n = 13). ET-1 was measured with specific radioimmunoassay after concentrating the sample with solid phase extraction. Pretreatment plasma ET-1 (1.28 +/- 0.36 pmol/ml, mean +/- SD) in the whole study group decreased (p < 0.01) to 1.05 +/- 0.26 pmol/ml at 6 months and to 1.10 +/- 0.32 pmol/ml at 12 months of treatment. A subgroup analysis between the two HRT regimens revealed no significant differences in the response of plasma ET-1 to HRT. These first data on HRT-induced reduction in plasma ET-1 may provide a new explanation for the cardiovascular protection by HRT.

17 beta-estradiol stimulates prostacyclin, but not endothelin-1, production in human vascular endothelial cells

The exact mechanisms by which estrogens protect against occlusive vascular disorders are not known. One possibility could be an effect on vascular endothelial vasoactive compounds, such as vasodilatory prostacyclin (PGI2) and vasoconstrictory endothelin (ET-1). Here we report on the effect of 17 beta-estradiol on the synthesis of PGI2 and ET-1 in cultured human umbilical vein endothelial cells. These cells were incubated in the absence (control) and presence of 17 beta-estradiol (0.001-1 mumol/L) for 3-24 h with serum (10%) or without serum. The release of PGI2, as assessed by its metabolite 6-keto-prostaglandin F1 alpha, and that of ET-1, were assessed by RIA. 17 beta-Estradiol (0.01-0.1 mumol/L) predissolved in ethanol (final concentration, 0.01%) increased PGI2 production by 26-30% in endothelial cells incubated without serum. This increase in PGI2 production was enhanced up to 66% when 17 beta-estradiol (1 mumol/L) was encapsulated within beta-cyclodextrin. The stimulation of PGI2 production was detectable after 12 h of incubation. The 17 beta-estradiol-induced stimulation of PGI2 production was blocked in dose-dependent manner by antiestrogenic tamoxifen. 17 beta-Estradiol failed to affect the production of PGI2 if the endothelial cells were incubated with serum and had no effect on ET-1 production under any conditions. 17 beta-Estradiol-induced stimulation of vasodilatory and antiaggregatory PGI2 production without a concomitant change in vasoconstrictory ET-1 production may provide one explanation for the ability of estradiol to maintain vascular health and protect against vascular disorders.

Prostacyclin and thromboxane in pregnant and nonpregnant women in response to exercise

OBJECTIVES

To compare the effects of a 30-minute standardized submaximal exercise test on the urinary excretion of the metabolites of prostacyclin and thromboxane A2 in healthy pregnant and nonpregnant women.

METHODS

Time-fixed urine samples were collected before, during, and after the exercise test from nine pregnant and six nonpregnant women, and the samples were assayed for 6-keto-prostaglandin (PG) F1 alpha and 2,3-dinor-6-keto-PGF1 alpha (prostacyclin metabolites), as well as for thromboxane B2 and 2,3-dinor-thromboxane B2 (thromboxane A2 metabolites) by high-pressure liquid chromatography and radioimmunoassay.

RESULTS

Pregnancy itself was associated with a 3.6-4.3-fold rise in prostacyclin excretion, but with no significant change in thromboxane output. The exercise caused stimulation in both prostacyclin and thromboxane excretion. In response to exercise, the maximal rise in 6-keto-PGF1 alpha output was significantly larger among the pregnant subjects, but when compared with its pre-exercise excretion on a relative percentage scale, the range of rise in 6-keto-PGF1 alpha output (58-73%) was comparable in pregnant and nonpregnant subjects. Furthermore, excretion of 2,3-dinor-6-keto-PGF1 alpha rose similarly in the two study groups (68-166%) in response to exercise. The exercise caused a 2.3-fold rise in the output of thromboxane B2 excretion in both pregnant and nonpregnant women, but it stimulated (by a twofold rise) the excretion of 2,3-dinor-thromboxane B2 only in pregnant women.

CONCLUSION

Physical activity may stimulate vasoactive prostacyclin and thromboxane excretion during pregnancy. Such changes may play a role in the regulation of blood flow during exercise.

Serum lipoproteins, insulin, and urinary prostanoid metabolites in normal and hypertensive pregnant women

OBJECTIVE

To determine if hyperinsulinemia, hypertension, hypertriglyceridemia, and low levels of high-density lipoprotein (HDL) cholesterol are present in women with pregnancy-induced hypertension or preeclampsia.

METHODS

Serum concentrations of insulin, uric acid, total and lipoprotein cholesterol, triglyceride, and apolipoproteins A-I and B were measured in 31 women with pregnancy-induced hypertension (eight with proteinuria) and in 21 healthy, pregnant, weight-matched controls at 30-39 weeks' gestation. The urinary excretion of the stable metabolites of prostacyclin (PGI2) (6-keto-prostaglandin [PG] F1 alpha and 2,3-dinor-6-keto-PGF1 alpha) and thromboxane A2 (TxA2) (thromboxane B2 and 2,3-dinor-thromboxane B2) was assessed in 17 women with pregnancy-induced hypertension and in eight controls.

RESULTS

Women with pregnancy-induced hypertension exhibited 18% lower mean serum HDL2 cholesterol levels (0.9 versus 1.1 mmol/L, P < .05) and 65% higher mean triglyceride levels (3.3 versus 2.0 mmol/L, P < .05) compared to controls, whereas other serum lipid and apolipoprotein values did not differ significantly in the two groups. Mean serum insulin levels (13.3 versus 6.5 mU/L, P < .01) and uric acid levels (339.7 versus 231.2 mumol/L, P < .01) in patients with pregnancy-induced hypertension were significantly higher than those in the controls. Urinary output of PGI2 metabolites was reduced by 35-45% in patients with pregnancy-induced hypertension, whereas no differences were seen in the excretion of TxA2 metabolites. Serum HDL2 cholesterol concentrations correlated positively with 2,3-dinor-6-keto-PGF1 alpha excretion, and serum triglyceride concentrations correlated positively with 2,3-dinor-thromboxane B2 excretion. In addition, insulin levels correlated positively with triglyceride levels but negatively with HDL2 cholesterol concentrations.

CONCLUSION

The metabolic characteristics (hypertriglyceridemia, hyperinsulinemia, hyperuricemia, low HDL2 cholesterol) in pregnancy-induced hypertension resemble the main features of the "insulin resistance syndrome." This may result in endothelial cell dysfunction as evidenced by PGI2 suppression.

Serum transferrin receptor and erythropoiesis in children with newly diagnosed acute lymphoblastic leukemia

Thirty-five children with acute lymphoblastic leukemia were monitored weekly during the first 12 weeks of chemotherapy. The transferrin receptor (TfR) concentration was 2.8 +/- 0.2 mg/l (mean +/- S.E.M.) at diagnosis, decreased up to 3 weeks, and then increased reaching a maximal level at 8 weeks. The mean values for reticulocyte counts followed a similar pattern. In contrast, serum erythropoietin and ferritin levels were generally high. Those patients whose erythropoiesis was more accelerated had higher serum TfR concentrations. We conclude that among these patients the TfR level reflected the rate of erythropoiesis and was independent of the level of erythropoietin.

Erythropoiesis of very low-birth-weight infants dependent on prenatal growth rate and protein status

This study investigated erythropoiesis in very low-birth-weight infants with special reference to the role of protein status in the regulation of erythropoiesis in 22 appropriate- and 11 small-for-gestational-age infants. Blood samples were drawn at three and six weeks of age. The serum concentrations of erythropoietin, estimated by a solid-phase enzyme immunoassay, were similar in the two groups at both study ages. The total circulating erythrocyte volume and the serum concentration of prealbumin were higher in the appropriate- than in the small-for-gestational-age infants at three and six weeks of age. The former group had a better protein status, although their protein intake was similar or lower. We conclude that erythropoiesis in very low-birth-weight infants is influenced more by protein status and prenatal growth than by serum concentration of erythropoietin.

Establishing reference values from adults: recommendation on procedures for the preparation of individuals, collection of blood, and handling and storage of specimens. Committee on Reference Values of the Scandinavian Society for Clinical Chemistry

The concentrations of blood components are influenced by a number of preanalytical factors, the importance of which varies [1]. Therefore it is necessary to standardize the specimen collection, as was done by the Committee on Reference Values of the Scandinavian Society for Clinical Chemistry and Clinical Physiology, which in 1975 published its recommendation on the production of reference values in clinical chemistry [2]. It was the very first recommendation of its kind. Since then, new information has accumulated, and it has become necessary to revise the part concerning the preparation of subjects for blood collection, the collection procedure itself, and the subsequent handling of the specimen. Also, The International Federation of Clinical Chemistry (Expert Panel on Theory of Reference Values) has produced its own recommendation [3]. The recommendation described below replaces pp. 39-44 of the former Scandinavian recommendation [2]. The procedure described below is designed for the collection of specimens for the measurement of the majority of components in blood and specimen collection from the cubital vein is described. It can be easily adapted for the collection of blood from other vessels [4]. Certain laboratory investigations require a special protocol. In that case, the preparation of the subject prior to and during specimen collection as well as the procedure itself should be described in sufficient detail to permit reproduction by adequately trained personnel. In any project designed to produce reference values the same protocol for the preparation of individuals and specimen collection should be used throughout the project. The protocol should be described in detail. Thus, it is not satisfactory to state only that the present recommendation was followed. Each section of the recommendation is followed by a check list for points which should be taken into account.

Low dose aspirin in hypertensive pregnant women: effect on pregnancy outcome and prostacyclin-thromboxane balance in mother and newborn

OBJECTIVE

To study the effect of daily treatment with 50 mg of aspirin (ASA) on the hypertensive pregnancy complications and on the production prostacyclin (PGI2) and thromboxane A2 (TxA2) in high risk pregnant women and their infants.

DESIGN

Placebo controlled prospective study.

SETTING

Departments of Obstetrics and Gynaecology, University of Helsinki, University of Oulu and Central Hospital of Middle Finland, Finland.

SUBJECTS

Two hundred and eight pregnant women with pre-existing hypertension or a history of severe preeclampsia in their previous pregnancy. Prostanoids were studied in a subgroup of 18 women.

INTERVENTIONS

The women were randomised to receive ASA (50 mg/day, n = 103) or placebo (n = 105) from the mean of 15 weeks gestational age to delivery. The exacerbation of pre-existing hypertension or the appearance of hypertension in previously normotensive women, the appearance of proteinuria and fetal growth were the main end points, but some other clinical characteristics were also recorded. Urinary excretion of PGI2 and TxA2 metabolites by mothers and infants and their production in umbilical arteries in vitro were also studied.

RESULTS

Two women (one in both groups) had miscarriages, and one pregnancy was terminated for fetal anencephaly (ASA group). In addition, seven women discontinued the treatment due to urticaria (two women in ASA group), increased activity of aspartate amino transferase in serum (one woman in both groups), or increased bleeding time (one woman in ASA group, two women in placebo group), and one woman in the placebo group was lost from follow-up. Thus the end points could be assessed in 97 women taking ASA and 100 women taking placebo. ASA did not diminish the rate of the rise of blood pressure without (12 vs 14, respectively) or with proteinuria (9 vs 11), but fetal haemodynamic disturbances as assessed by Doppler equipment (1/44 vs 6/45 women studied, P = 0.05) and need for treatment in neonatal intensive care unit (10 vs 21, P = 0.04) were more rare in ASA group. ASA tended to increase the birthweight of the newborn (3348 +/- 707 g vs 3170 +/- 665 g, mean +/- SD, P = 0.07), but two perinatal deaths occurred in ASA group. ASA prolonged the bleeding time of the mother (435 s, 210-998 s (geometric mean, range) vs 349 s, 210-690 s, P = 0.02), but caused no extra blood loss during delivery, nor affected neonatal hemostasis. In a subgroup of mothers (ASA, n = 10; placebo, n = 8), ASA inhibited more than 90% of platelet TxA2-production, and caused a 65 to 80% decrease in the urinary excretion of TxA2 metabolites, but no decrease in the urinary excretion of PGI2 metabolites.

CONCLUSIONS

ASA did not prevent the rise of maternal hypertension, but improved fetal haemodynamic performance and reduced the need of intensive neonatal care. It inhibited strongly maternal thromboxane A2 but not PGI2 production and thus shifted the balance between PGI2/TxA2 to the dominance of the vasodilatory, anti-aggregatory side.

Serum transferrin receptor for assessment of iron status in healthy prepubertal and early pubertal boys

A recently introduced test measures the concentration of transferrin receptor (TfR) in serum, which increases shortly after the onset of iron deficiency. In adults this increase reflects the degree to which tissue iron availability is impaired. We developed a fluoroimmunoassay to quantify TfR. The purpose of this study was to evaluate the role of TfR as an index of iron sufficiency in 62 healthy prepubertal or early pubertal boys. The mean concentration of serum TfR was 3.8 (-1 SEM = 3.6, +1 SEM = 3.9) mg/L. No associations were observed between the serum TfR and the concentration of Hb, the values of packed cell volume, reticulocyte production index, mean corpuscular Hb, mean corpuscular volume, or the concentrations of serum iron, transferrin, or ferritin. Because none of the subjects had signs of iron deficiency, we determined the 95% reference intervals for Hb, red blood cell indices, and the above-mentioned serum concentrations. The reticulocyte count and reticulocyte production index were higher than expected. Our results indicated that the individual concentration of TfR in serum does not depend on any of the several other parameters of iron status in a group of healthy individuals.

Dietary supplementation with primrose oil or fish oil does not change urinary excretion of prostacyclin and thromboxane metabolites in pre-eclamptic women

To study whether balance between antiaggregatory, vasodilatory prostacyclin (PGI2) and proaggregatory, vasoconstrictory thromboxane A2 (TXA2) could be affected by dietary manipulation, 18 pre-eclamptic women were treated in randomized order between 31 and 36 weeks of gestation either with primrose oil (n = 7), with fish oil (n = 5), or with placebo (n = 6). Urinary excretions of the degradation products of PGI2 (6-keto-PGF1 alpha, 2,3-dinor-6-keto-PGF1 alpha) and TXA2 (TXB2, 2,3-dinor-TXB2) were measured in 24 h urines before and serially during the supplementation. Fatty acid supplementation did not affect urinary prostanoid excretions or clinical signs of pre-eclampsia.

Marathon run stimulates more prostacyclin than thromboxane synthesis and differently in men and women

To study the effect of strenuous physical exercise on the balance between vasodilatory and antiaggregatory prostacyclin (PGI2) and its endogenous antagonist thromboxane A2 (TxA2), we measured the urinary output of two metabolites of PGI2 (6-keto-prostaglandin F1 alfa, 6-keto, and 2,3-dinor-6-keto), as well as two metabolites of TxA2 (thromboxane B2, TxB2, and 2,3-dinor-TxB2) ten days before, during and one, three and five days after a marathon run by 15 women and ten men. The basal urinary outputs of women and men were similar. In women, 6-keto excretion increased 10-fold (p < 0.001) and in men 30-fold (p < 0.05) during the run, and 2,3-dinor-6-keto increased 2-fold in women (p < 0.05) and 7-fold in men (p < 0.05). During the run, TxB2 output increased only in women (3-fold, p < 0.05) and 2,3-dinor-TxB2 only in men (4-fold, p < 0.05). The marathon-induced changes lasted maximally one day. The greater PGI2-than TxA2-stimulation during marathon run may be involved with the favorable effects on the cardiovascular system of physical exercise.

Production of prostacyclin and thromboxane in lupus pregnancies: effect of small dose of aspirin

OBJECTIVES

To find out whether the tendency toward poor outcome in lupus pregnancies could be explained by changes in prostacyclin/thromboxane production, to relate these changes to the presence of antiphospholipid antibodies, and to study the potential benefits of low-dose aspirin.

METHODS

We followed the urinary output of prostacyclin metabolites (6-keto-prostaglandin [PG]F1 alpha, 2,3-dinor-6-keto-PGF1 alpha) and thromboxane metabolites (thromboxane B2, 2,3-dinor-thromboxane B2) using high-pressure liquid chromatography followed by radioimmunoassay. We studied 14 pregnant women with systemic lupus erythematosus (SLE), of whom six had detectable antiphospholipid antibodies. The patients were randomized by a computerized program to receive either 50 mg aspirin daily (six women) or placebo (eight women). Nine healthy pregnant women served as controls.

RESULTS

The production of prostacyclin was normal in early pregnancy in SLE patients but was reduced during late gestation in those without antiphospholipid antibodies. The production of thromboxane was increased in SLE patients compared with controls, and this increase was highest (two-to threefold rise) when antiphospholipid antibodies were detectable. Aspirin eliminated thromboxane dominance without affecting prostacyclin production.

CONCLUSION

These data suggest that the presence of antiphospholipid antibodies in SLE patients may trigger thromboxane dominance, possibly contributing to the adverse outcome of these pregnancies. This thromboxane dominance can be eliminated with aspirin.

Human serum, plasma, and platelets stimulate prostacyclin and endothelin-1 synthesis in human vascular endothelial cells

Prostacyclin (PGI2), a powerful vasodilatory prostanoid, and endothelin-1 (ET-1), a potent vasoconstrictive peptide, are produced by vascular endothelial cells. We show that human serum (10%) caused a 3.2-fold stimulation both in PGI2 and ET-1 synthesis in human endothelial cells cultured from umbilical veins, and human plasma (10%) stimulated productions of both 1.6- and 1.7-fold, respectively. In addition, releasates from thrombin-activated platelets (20 x 10(9) platelets/l) caused a 1.9-fold increase in PGI2 and a 1.4-fold increase in the ET-1 synthesis. Releasates from frozen-thawed and sonicated platelets (20 x 10(9) platelets/l) caused a 3.6-fold increase in PGI2 release but did not affect ET-1 production. We thus conclude that, in normal situation, endothelial stimulating activity present in plasma perhaps plays a role in the regulation of endothelial function, whereas platelet-derived activity in serum may be important at site of thrombosis.