Reference intervals and developmental changes in urinary prostanoid excretion in healthy newborns, infants and children

Urinary PGE2 metabolite levels in hospitalised infants with infections compared to age-matched controls

AIM

To determine the urinary tetranor-prostaglandin E₂ metabolite in healthy infants and in hospitalised infants with upper and lower respiratory tract as well as gastrointestinal infections.

METHODS

A prospective cross-sectional study to determine baseline concentrations of urinary tetranor-prostaglandin E₂ metabolite was conducted in 81 healthy infants aged one week to one year and in 142 hospitalised infants with infections. Prostaglandin metabolite levels were measured by liquid chromatography tandem mass spectrometry.

RESULTS

In healthy infants, urinary prostaglandin E₂ metabolite levels decreased with age and did not differ between girls and boys. Infections of the lower respiratory (n = 78) and gastrointestinal tract (n = 12) correlated with increased levels of the prostaglandin E₂ metabolite. In contrast, infants hospitalised with upper respiratory tract infections (n = 23) exhibited similar levels as healthy, age-matched controls. Lower prostaglandin E₂ levels were found after treatment with acetaminophen in hospitalised children. Prostaglandin E₂ metabolite levels did not correlate with length of hospitalisation or need for respiratory support.

CONCLUSION

This study first provides normal levels of urinary prostaglandin E₂ metabolite in infants and secondly demonstrates elevated levels in hospitalised children with lower respiratory tract and gastrointestinal infections.

Prostaglandin E-major urinary metabolite as a noninvasive surrogate marker for infantile necrotizing enterocolitis

BACKGROUND

Early definitive diagnosis of necrotizing enterocolitis (NEC) based on Bell's staging criteria is difficult because there are few observable changes on abdominal imaging and blood chemistry tests at the onset of the disease.

PURPOSE

To investigate whether prostaglandin E-2 major urinary metabolite (PGE-MUM) can be a useful surrogate marker reflecting the disease state and severity of NEC in infants.

METHODS

Infants were enrolled in this study between January 2014 and December 2016. NEC diagnosis was based on Bell's staging criteria > Stage II or necrotic bowel observed at surgery. After diagnosis, PGE-MUM level was measured and compared with that of the other disease and healthy infant groups.

RESULTS

Median PGE-MUM value was highest in the NEC group (576 [65-3672] μg/g•Cre/BSA × 1000), followed by the other disease group (94 [57-296] μg/g•Cre/BSA × 1000) and the healthy infant group (19 [10-44] μg/g•Cre/BSA × 1000) (sensitivity: 92.3%, specificity: 81.5%, accuracy: 85.0%; p < 0.01). PGE-MUM level correlated with improved status of NEC, length of necrotic intestine, and Bell's staging criteria.

CONCLUSIONS

PGE-MUM level may be a useful surrogate biomarker reflecting the disease state of NEC. The method of urine sample collection is also advantageous, being noninvasive for infants. This is the first study reporting PGE-MUM level in NEC.

TYPE OF STUDY

Study of diagnostic test.

LEVEL OF EVIDENCE

LEVEL II.

Evaluation of urinary prostaglandin E2 metabolite as a biomarker in infants with fever due to viral infection

We have investigated the clinical feasibility of the major urinary metabolite of prostaglandin (PG) E2, tetranor-PGEM, as a biomarker of inflammation in infants with fever. We tested two different and clinically relevant sampling methods, using self-adhesive urinary bags or gauze pads, with respect to stability of tetranor-PGEM and ease of sampling from infants. Liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis was used to quantify tetranor-PGEM in urine, and different normalization parameters, i.e., urinary creatinine and body surface area, were investigated. To study inflammation, infants (1 month-1 year) that were hospitalized with fever of unknown origin at admittance (n=14) were compared to age-matched healthy controls (n=14). Levels of urinary tetranor-PGEM in infants with viral induced fever were increased compared to controls (102.4±56.2 vs. 37.0±21.6pmol/ml/m(2) body surface area, p<0.001). We conclude that urinary tetranor-PGEM is a potential non-invasive biomarker of inflammation in infants.

Urinary prostaglandin E2 in the newborn and infant

Prostaglandin E(2) (PGE(2)) belongs to a family of biologically active lipids derived from the 20-carbon essential fatty acids. Renal PGE(2) is involved in the development of the kidney; it also contributes to regulate renal perfusion and glomerular filtration rate, and controls water and electrolyte balance. Furthermore, this mediator protects the kidney against excessive functional changes during the transition from fetal to extrauterine life, when it counteracts the vasoconstrictive effects of high levels of angiotensin II and other mediators. There is evidence that PGE(2) plays an important pathophysiological role in neonatal conditions of renal stress, and in congenital or acquired nephropaties. Thus, measurement of urinary PGE(2) as an index of renal synthesis of this primary prostaglandin may represent a non-invasive and sensitive method of investigating the homeostatic function of the kidney in early life. The aim of this literature review is to examine urinary PGE(2) as a non-invasive marker of renal homeostasis in the newborn and infant under both physiological and pathological conditions, or during treatments with widely used, potentially toxic drugs.

Increased systolic blood pressure with rofecoxib in congenital furosemide-like salt loss

BACKGROUND

To analyse whether congenital furosemide- or thiazide-like renal salt loss protects against the potential prohypertensive effects of two cyclooxygenase (COX) inhibitors: rofecoxib, a COX-2 selective inhibitor, and indomethacin, an unselective COX-inhibitor.

METHODS

In a retrospective analysis, the effects of rofecoxib and indomethacin on blood pressure (bp: transformed into age-independent standard deviation scores (SDS) values), creatinine clearance (CRC), fractional excretion of sodium (FeNa), and renal excretion of systemic prostaglandins were studied in 28 patients with a genetically proven congenital hypokalaemic salt-losing tubulopathy (SLT) (11 female and 17 male, age: 2-25 years), 19 with a furosemide-like SLT, and nine with a thiazide-like SLT.

RESULTS

In furosemide-like SLT patients, systolic SDS bp values were significantly higher with rofecoxib (1.03 +/- 0.16 SDS, n = 107) compared with indomethacin (0.56 +/- 0.09 SDS, n = 282; P = 0.007, 95% CI: 0.12-0.8). Without the drugs, systolic SDS bp values were elevated by 0.63 +/- 0.11 SDS, n = 164. Both drugs reduced renin and aldosterone-plasma levels to a similar extent. SDS values were significantly correlated with the excretion of the vasoconstrictor thromboxane (T x B2) (R2: 0.038, P = 0.021, n: 159), but not with CRC or FeNa. Blood pressure was not increased in thiazide-like SLT patients treated with rofecoxib.

CONCLUSION

Congenital furosemide-like renal salt loss does not protect against the prohypertensive effects of rofecoxib. The positive correlation between bp SDS values with T x B2 but not with FeNa or CRC point towards an altered vascular homeostasis as one mechanism increasing blood pressure.

Perinatal management of a preterm neonate affected by hyperprostaglandin E2 syndrome (HPS)

BACKGROUND

Neonates affected by hyperprostaglandin E(2) syndrome (HPS) present with severe polyuria. Both urinary losses as well as prostaglandin synthesis inhibitors may precipitate acute renal failure (ARF).

AIM

Our goal was to maintain euvolaemia by replacement of urinary losses.

PATIENT

Our patient was born prematurely with a family history typical of HPS. Urinary salt and water losses and PGE(2) excretion were determined in 2- to 4-h intervals. Salt and water were replaced accordingly.

RESULTS

Within the first 48 h, urinary losses and PGE(2) increased continuously to 50 ml/kg/h and 374 ng/h/1.73 m(2), respectively. Following exposure to 0.05-0.5 mg/kg/d indomethacin, urinary output decreased steadily to 10-15/ml/kg/h.

CONCLUSION

In euvolaemic preterm neonates with HPS and the need for excessive replacement of salt and water, inhibition of renal PGE(2) excretion with indomethacin effectively reduces polyuria and natriuresis without acutely compromising renal function.

Salt handling in the distal nephron: lessons learned from inherited human disorders

The molecular basis of inherited salt-losing tubular disorders with secondary hypokalemia has become much clearer in the past two decades. Two distinct segments along the nephron turned out to be affected, the thick ascending limb of Henle's loop and the distal convoluted tubule, accounting for two major clinical phenotypes, hyperprostaglandin E syndrome and Bartter-Gitelman syndrome. To date, inactivating mutations have been detected in six different genes encoding for proteins involved in renal transepithelial salt transport. Careful examination of genetically defined patients (“human knockouts”) allowed us to determine the individual role of a specific protein and its contribution to the overall process of renal salt reabsorption. The recent generation of several genetically engineered mouse models that are deficient in orthologous genes further enabled us to compare the human phenotype with the animal models, revealing some unexpected interspecies differences. As the first line treatment in hyperprostaglandin E syndrome includes cyclooxygenase inhibitors, we propose some hypotheses about the mysterious role of PGE2in the etiology of renal salt-losing disorders.

Induction of microsomal prostaglandin E2 synthase in the macula densa in children with hypokalemic salt-losing tubulopathies

In hyperprostaglandin E syndrome (HPGES) and classic Bartter syndrome (cBS), tubular salt and water losses stimulate renin secretion, which is dependent on enhanced cyclooxygenase-2 (COX-2) enzymatic activity. In contrast to other renal COX metabolites, only prostaglandin E(2) (PGE(2)) is selectively up-regulated in these patients. To determine the intrarenal source of PGE(2) synthesis, we analyzed the expression of microsomal PGE(2) synthase (mPGES; EC: 5.3.99.3), whose product PGE(2) has been shown to stimulate renin secretion in vitro. Expression of mPGES was analyzed by immunohistochemistry in eight patients with HPGES, in two patients with cBS, and in six control subjects. Expression of mPGES immunoreactive protein was observed in cells of the macula densa in five of eight HPGES patients and in one of two cBS patients. Expression of mPGES immunoreactive protein was not observed in cells associated with the macula densa in kidneys from control subjects without a history consistent with activation of the renin angiotensin system. Co-induction of COX-2 and mPGES in cells of the macula densa suggests that PGE(2) activates renin secretion in humans.

Low-dose aspirin in pregnancy: maternal and neonatal aspirin concentrations and neonatal prostanoid formation

OBJECTIVE

To evaluate maternal and neonatal plasma concentrations of acetylsalicylic acid and salicylic acid and the neonatal endogenous prostanoid formation during low-dose aspirin prophylaxis (LDA; 100 mg daily) in pregnant women.

METHODS

Concentrations of acetylsalicylic acid and salicylic acid in maternal plasma after at least 4 weeks of LDA (n = 14) and in umbilical cord plasma of newborns after maternal LDA (n = 7) were determined by gas chromatography-mass spectrometry. Platelet and renal formation of thromboxane A2 and the formation of prostaglandin E2 and prostacyclin were evaluated in vivo by quantification of index metabolites in plasma and urine by gas chromatography-mass spectrometry in neonates after maternal LDA (n = 14) and in a control group.

RESULTS

In the pregnant women, acetylsalicylic acid and salicylic acid concentrations rapidly increased after ingestion of LDA. Acetylsalicylic acid was completely eliminated within 4 hours, whereas salicylic acid was detected with low concentrations at 18 and 21 hours after dosing. In the neonates, acetylsalicylic acid was not detected. Salicylic acid was detected in 1 infant only. Platelet thromboxane A2 formation in the newborn infants was significantly suppressed but recovered within 2 to 3 days after discontinuation of LDA. Renal thromboxane A2 formation and the formation of prostaglandin E2 and prostacyclin were not affected by LDA.

CONCLUSION

In pregnant women who are treated with LDA, acetylsalicylic acid is not completely inactivated in the portal circulation but reaches the uteroplacental circulation and exerts antiplatelet effects in the fetus and newborn.

Role of renal PGE2 in the adaptation from foetal to extrauterine life in term and preterm infants

Urinary PGE(2) concentrations were assayed using a new EIA method, in 16 preterm and 18 term neonates at birth and 3 days later, since there is evidence that PGE(2) in urine are likely to reflect their renal generation and then could be correlated with kidney maturation or renal problems. PGE(2) concentrations were not different at birth (1.50+/-1.12 vs 1.56+/-1.94 ng/day), while resulted significantly higher in preterms, compared to terms, three days after birth (2.22+/-1.23 vs 1.39+/-0.79 ng/day). This increase in daily PGE(2) excretion observed only in preterm neonates could be due to an increased renal biosynthesis as a mechanism of compensatory response to prevent further decrements in renal plasma flow, since prostanoids play an important role in protecting the immature kidney from high levels of angiotensin II. Otherwise, the passive reabsorption of PGE(2) along the distal nephron could be altered because of kidney immaturity. The measurement of PGE(2) in urine of neonates, particularly prematures, could be useful to provide a better understanding of the homeostatic function of the kidney in the phase of adaptation to extra-uterine life.

Hypokalemic salt-losing tubulopathy with chronic renal failure and sensorineural deafness

OBJECTIVE

To characterize a rare inherited hypokalemic salt-losing tubulopathy with linkage to chromosome 1p31.

METHODS

We conducted a retrospective analysis of the clinical data for 7 patients in whom cosegregation of the disease with chromosome 1p31 had been demonstrated. In addition, in 1 kindred, prenatal diagnosis in the second child was established, allowing a prospective clinical evaluation.

RESULTS

Clinical presentation of the patients was homogeneous and included premature birth attributable to polyhydramnios, severe renal salt loss, normotensive hyperreninemia, hypokalemic alkalosis, and excessive hyperprostaglandin E-uria, which suggested the diagnosis of hyperprostaglandin E syndrome/antenatal Bartter syndrome. However, the response to indomethacin was only poor, accounting for a more severe variant of the disease. The patients invariably developed chronic renal failure. The majority had extreme growth retardation, and motor development was markedly delayed. In addition, all patients turned out to be deaf.

CONCLUSION

The hypokalemic salt-losing tubulopathy with chronic renal failure and sensorineural deafness represents not only genetically but also clinically a disease entity distinct from hyperprostaglandin E syndrome/antenatal Bartter syndrome. A pleiotropic effect of a single gene defect is most likely causative for syndromic hearing loss.

Urinary PGE(2) concentrations measured by a new EIA method in infants with urinary tract infections or renal malformations

In this work PGE(2)concentrations were measured by a new EIA method in the urine of infants (mean age: 9.35+/-4.24 months) with recurrent urinary tract infections or renal malformations. Compared to healthy subjects, PGE(2)excretion rates resulted significantly higher in both pathological groups, in particular in subjects with obstructive uropathies (29.55+/-8.12 vs 18.37+/-4.64 pg/ml). We did not find any age- or pH-dependent difference in urinary excretion of PGE(2); none of the examined indices of renal function showed any significant relationship to PGE(2). These results suggest that this parameter, measured non-invasively in the urine, could help in the differential diagnosis between obstructive vs non-obstructive dilatation and in monitoring renal function in presence of recurrent UTI episodes.

Neonatal urinary prostanoid excretion

Urinary excretion of prostanoids prostaglandin E2 (PGE2), PGE-M (7alpha-hydroxy-5,11-diketo-2,3,4,5,20-penta-19-carboxyprostano ic acid), 6-keto-PGF1alpha, 2,3-dinor-6-keto-PGF1alpha, thromboxane B2 (TxB2) 2,3-dinor-TxB2 and 11-dehydro-TxB2 was determined by gas chromatography/mass spectrometry in preterm and term infants to show that there is an age-dependent excretion rate of the above prostanoids in infants this young. Group I included premature children with normal postnatal development, Groups II and III included term children who were admitted in the neonatal period for observation because of feeding problems but who were subsequently found to be completely healthy. We present normal data of three primary prostanoids and four prostanoid metabolites. In Group I, excretion rates of 2,3-dinor-TxB2 were significantly lower than in Group II (P = 0.04) and in Group III (P = 0.05). Furthermore, the excretion rate of 11-dehydro-TxB2 in group I was significantly lower than in Group II (P = 0.05). We found no significant age-dependent differences between the three groups in excretion rates of PGE2, PGE-M, 6-keto-PGF1alpha, 2,3-dinor-6-keto-PGF1alpha, and TxB2.

Treatment of childhood hypophosphatasia with nonsteroidal antiinflammatory drugs

Hypophosphatasia (HP) is an inborn error of metabolism that is characterized by reduced bone mineralization. The aim of this investigation was to evaluate treatment of incapacitating lower limb pain in patients with childhood HP using nonsteroidal antiinflammatory drugs (NSAID). All patients (seven boys; age 32 months to 16 years) presented with delayed walking, the typical waddling gait, muscular weakness of the lower limbs, and a limited walking distance. Six patients had severe diffuse lower limb pain following physical activity and were therefore treated with NSAID. The benefit of this treatment was evaluated clinically and by measurement of renally (PGE2) and systemically (PGE-M) derived prostaglandins (PG) in urine before and during therapy. After treatment with NSAID all six patients showed marked clinical improvement with reduced pain, increased muscle strength, and a normalized walking distance. Levels of PGE-M, which had been elevated in four patients prior to therapy, returned to normal. The use of NSAID in childhood HP should be considered as a possible therapeutic approach because the quality of life in these patients is markedly impaired by pain of the limbs. Elevated PG might play a role in the bone metabolism of HP patients.

An imbalance between prostacyclin and thromboxane in relation to cerebral blood flow in neonates with maternal preeclampsia

OBJECTIVE

A disturbance of prostacyclin (PGI2) and thromboxane A2 (TXA2) balance has been reported in preeclampsia. However, little is known about the concentrations of these prostanoids in neonates born to preeclamptic pregnant women. The purpose of this study is to determine whether the PGI2 and TXA2 concentrations are altered and whether the prostanoid balance correlates to the cerebral blood flow in neonates born to preeclampsia.

METHODS

Spontaneously voided urine samples were collected from 20 neonates of normotensive and 16 neonates of preeclamptic women during the first 24 h after birth. We measured by radioimmunoassay the concentrations of urinary 6-keto-prostaglandin F1alpha (6-keto-PGF1alpha) and 11-dehydro-thromboxane B2 (11-dehydro-TXB2), respectively. Blood flow velocity in the middle cerebral artery was studied by pulsed Doppler ultrasonography in the neonates between 17 and 38 h after birth.

RESULTS

There was no significant difference between the urinary 6-keto-PGF1alpha in the neonates of mothers with and without preeclampsia (median, 5.3 vs. 3.6 ng/mg of creatinine). In contrast, the urinary 11-dehydro-TXB2 and the ratio of 11-dehydro-TXB2 to 6-keto-PGF1alpha in the neonates of mothers with preeclampsia were significantly lower as compared with the neonates without preeclampsia, respectively (13.7 vs. 20.6 ng/mg of creatinine and 3.0 vs. 5.2, median). The resistance index in the middle cerebral artery was significantly reduced in the neonates with preeclampsia than without preeclampsia (0.67 +/- 0.01 vs. 0.74 +/- 0.02, mean +/- SEM).

CONCLUSIONS

There was an association between maternal preeclampsia and the imbalance in the neonatal urinary excretion of PGI2 and TXA2 metabolites. This imbalance may contribute to the regulation of cerebral blood flow.

Long-chain polyunsaturated fatty acids and eicosanoids in infants--physiological and pathophysiological aspects and open questions

Eicosanoids are highly active lipid mediators in physiologic and pathologic processes, with their effects ranging from cytoprotection and vasoactivity to modulation of inflammatory and proliferative reactions. Generation of eicosanoids can be affected by changes in the pools of their precursors, the long-chain polyunsaturated fatty acids (LCPUFA). Thus, dietary interventions such as supplementation of infant formula with specific n-3 and n-6 LCPUFA will alter formation as well as activity of the eicosanoids produced. This report summarizes the results and discussion of the workshop on "Eicosanoids and Polyunsaturated Fatty Acids in Infants." The intention of the workshop organizers was to give an overview of the role of eicosanoids in physiological and pathophysiological processes in infants, to discuss the implications that an increased n-3 and n-6 LCPUFA intake may have on eicosanoid generation, and to point out open questions and controversies for future research.

Prostacyclin concentrations and transitional circulation in preterm infants requiring mechanical ventilation

AIM

To describe the association between early postnatal prostacyclin concentrations in preterm infants; echocardiographic measurements of ductal diameter and ventricular output and clinical outcomes of intraventricular haemorrhage (IVH) and patent ductus arteriosus (PDA).

METHODS

Forty nine preterm infants born before 30 weeks of gestational age (median birthweight 980 g, median gestational age 27 weeks) underwent echocardiographic studies at 5, 12, 24 and 48 hours of postnatal age. Measurements included ventricular outputs and the ductal shunt diameter as a measure of the shunt size. Simultaneous measurements of blood pressures, mean airway pressure and inspired fraction of oxygen (FIO2) were recorded. A blood sample for the prostacyclin metabolite 6-ketoprostaglandin F1-alpha (6KPGF1 alpha) was taken at the 5 and 24 hour echocardiogram.

RESULTS

The mean 6KPGF1 alpha concentrations were higher than adult concentrations at 5 (515 pg/ml) and 24 (255 pg/ml) hours. There was no association with gestational age. Raised 6KPGF1 alpha concentrations were related to increased need for mechanical ventilation and severity of respiratory disease. At 5 hours, increased 6KPGF1 alpha concentrations were associated with larger PDA and at 24 hours with larger PDA and higher left ventricular output. Infants with higher 6KPGF1 alpha concentrations were more likely to develop clinically significant PDA. There was no association between early measurements of 6KPGF1 alpha and IVH.

CONCLUSIONS

Early postnatal prostacyclin concentrations are markedly raised in preterm infants, particularly in those with more severe lung disease. Raised 6KPGF1 alpha concentrations were associated with an increased ductal diameter and subsequent PDA, but not IVH.

Prostanoid formation during feeding of a preterm formula with long-chain polyunsaturated fatty acids in healthy preterm infants during the first weeks of life

The objective of this study was to evaluate the effect of conventional and long-chain polyunsaturated fatty acids (LCP)-enriched preterm formula on prostanoid formation in preterm infants during their first weeks of life. In a prospective, randomized, double-blind study, healthy infants received either formula enriched with LCP (n = 10), standard preterm formula (n = 10), or (expressed) breast milk (n = 10). Urine was sampled, and anthropometric measurements were taken at study entry and after the study period of 3 wk. In vivo formation of prostaglandin E2, thromboxane A2, and prostacyclin was evaluated by measuring the urinary excretion of the respective index metabolities by gas chromatography-mass spectrometry. There were no significant differences in urinary prostanoid excretion and anthropometric data between the groups at the end of the study period. We conclude that neither conventional formula nor supplementation of a preterm formula with LCP for a period of 3 wk substantially influence prostanoid formation in healthy preterm infants.

Measurements of urinary prostaglandins in young ovulatory women during the menstrual cycle and in postmenopausal women

The purpose of the present work was to study the prostaglandin excretion in young nonpregnant ovulatory women during the menstrual cycle on the one hand and in postmenopausal women on the other hand and to investigate the influence of female sex hormones (estradiol, progesterone) on urinary prostanoid excretion. Urinary excretion rates of prostaglandin E2 (PGE2), 6-keto-PGF1 alpha, thromboxane B2 (TxB2) and their metabolites PGE-M (11 alpha-hydroxy-9, 15-dioxo-2,3,4,5,20-pentanor-19-carboxyprostanoic acid), 2,3-dinor-6-keto-PGF1 alpha, 2,3-dinor-TxB2 and 11-dehydro-TxB2 were determined by gas chromatography-triple stage quadrupole mass spectrometry (GC/MS/MS) in 41 young non-pregnant women during the follicular phase and during the luteal phase and in 23 postmenopausal women. Excretion rates of all urinary prostanoids were not significantly different in the follicular phase when compared with the luteal phase. In contrast to the young ovulatory women, PGE2 and TxB2 were significantly higher in postmenopausal women. Concerning the other prostaglandins significant differences between these groups of women did not exist. Although serum levels of estradiol and progesterone were different in young and postmenopausal women, sex hormones have not been shown to correlate with prostaglandins. Our data do not suggest sex hormones to be responsible for the difference in the prostaglandin excretion in women of reproductive age and in women in the menopause. Further systematic investigations into age dependency of prostaglandin excretion in women are necessary.

Prostanoid biosynthesis in patients with cystic fibrosis

The urinary excretion rate (ng/h/1.73 m2) of prostanoids was determined with a capillary gas-liquid chromatographic mass spectrometric method in 19 patients with cystic fibrosis (CF) aged 1-29 years. Patients with CF showed an increased excretion of prostaglandin E2 metabolites (PGE-M) and thromboxane B2 and its metabolites at all ages. An imbalance in the excretion pattern of thromboxane B2 metabolites also suggested a relative impairment of beta-oxidation. There was no increased excretion of dinor-6-keto-PGF1 alpha, indicating normal prostacyclin biosynthesis. No correlation was found to genotype, clinical score, lung function or bacterial colonization but a significant negative relation was found between the main prostanoids in the urine and serum phospholipid levels of essential fatty acids. The results show that, contrary to the generally accepted decrease of prostanoid excretion in essential fatty acid deficiency, patients with CF increase their production parallel to the development of the deficiency. Since prostanoid synthesis is rate limited by arachidonic acid release, our data support a previously presented hypothesis about a pathological regulation of the release of arachidonic acid in CF.

Gas chromatography/negative ion chemical ionization triple quadrupole mass spectrometric determination and pharmacokinetics of 11 alpha-hydroxy-9,15-dioxo-2,3,4,5,20-pentanor-19-carboxyprostan oic acid in plasma

11 alpha-Hydroxy-9,15-dioxo-2,3,4,5,20-pentanor-19-carboxyprostanoic acid (PGE-M) was determined in plasma. Analysis was performed using an isotope dilution assay and gas chromatography/triple quadrupole mass spectrometry (GC/MS/MS). Basal levels of PGE-M were 64.05 +/- 34.17 pg/ml. After infusion of 120 micrograms prostaglandin E1 (PGE1) in six subjects in 15 min, maximum levels of PGE-M of 618.6 +/- 210.3 pg/ml were reached 20-45 min after the end of infusion. 3 h after the end of the infusion, plasma levels were close to the preinfusion levels. The pharmacokinetics of PGE-M in plasma were also determined. PGE-M has a half-life of 8.96 +/- 3.53 min for formation and 31.71 +/- 6.39 min for elimination. In addition to PGE-M, PGE1, 15-keto-PGE1 and PGE0 were also determined by GC/MS/MS.