Long-term outcome after allo-SCT: close follow-up on a large cohort treated with myeloablative regimens

We analyzed the late outcomes of 429 long-term survivors post allogeneic hematopoietic SCT (allo-HSCT) who received transplant in our center between 1981 and 2002, and were free of their primary disease for > or =2 years after allo-HSCT. Late recurrent primary malignancy was found in 58 (13.5%) patients and was the primary cause of late death. A total of 37 (8.6%) patients died of non-relapse causes at a median of 5.5 years (range, 2-15.6 years) post allo-HSCT. The major non-relapse causes of death were chronic GVHD (cGVHD), secondary malignancy and infection. The probabilities of OS and EFS were 85% (95% cumulative incidence (CI) (81-89%)) and 79% (95% CI (74-83%)) at 10 years, respectively. Long-term allo-HSCT survivors were evaluated for late complications (median follow-up, 8.6 years (range, 2.3-22.8 years)). cGVHD was diagnosed in 196 (53.1%) survivors. The endocrine and metabolic complications were hypogonadism in 134 (36.3%) patients, osteopenia/osteoporosis in 90 (24.4%), dyslipidemia in 33 (8.9%), hypothyroidism in 28 (7.6%) and diabetes in 28 (7.6%). Hypertension was diagnosed in 79 (21.4%), renal impairment in 70 (19.0%), depression in 40 (10.8%) and sexual dysfunction in 33 (8.9%) survivors. We conclude that in patients who receive allo-HSCT as treatment for hematological malignancy and who are free of their original disease 2 years post transplant, mortality is low and the probability of durable remission is high. Lifelong surveillance is recommended.

Positive impact of selective outpatient management of high-risk acute myelogenous leukemia on the incidence of septicemia

BACKGROUND

Curative intent chemotherapy for acute myelogenous leukemia (AML) leads to prolonged severe neutropenia, during which patients are highly susceptible to infection. Traditionally these high-risk patients were treated as inpatients. Our center recently implemented a selective ambulatory management policy for AML patients undergoing chemotherapy.

MATERIALS AND METHODS

A retrospective analysis was conducted to assess the occurrence of septicemia in AML patients treated over a 5 years period with curative intent chemotherapy. This review encompasses a change in policy from primarily inpatient care to selective outpatient management coupled with prophylactic antibiotic therapy.

RESULTS

A total of 294 patients, receiving 623 cycles of chemotherapy were identified. A significant decrease in septicemia was observed from the inpatient to outpatient cohort (22% to 13% P < 0.05), which correlated with the shift towards outpatient treatment of consolidation cycles. A shift from Gram-negative to Gram-positive organisms as the cause of septicemia was also detected in the outpatient cohort, likely due to the introduction of ciprofloxacin prophylaxis. No significant emerging resistance and no septicemia-related mortality were noted in the outpatient cohort.

CONCLUSION

The observed decrease in the incidence of septicemia in the ambulatory cohort adds supportive evidence to the feasibility of selective outpatient management of AML patients with respect to infectious complications.

Primary therapy for adults with T-cell lymphoblastic lymphoma with hematopoietic stem-cell transplantation results in favorable outcomes

BACKGROUND

Controversy exists regarding the role of high-dose therapy followed by stem-cell transplant (SCT) in the treatment of T-cell lymphoblastic lymphoma (T-LBL). We conducted an intention-to-treat analysis of the strategy of SCT as definitive treatment of T-LBL.

PATIENTS AND METHODS

From July 1987 to March 2005, 34 adults with T-LBL were diagnosed and treated in British Columbia. Treatment, before planned SCT, consisted of a non-Hodgkin's lymphoma (NHL)/acute lymphoblastic leukemia hybrid chemotherapy protocol (28 patients) or a standard NHL chemotherapy regimen (six patients).

RESULTS

Median follow-up of the 23 surviving patients is 51 months (range 13-142 months). Twenty-nine proceeded to SCT (four allogeneic, 25 autologous). For all 34 patients, 4-year overall survival (OS) and event-free survival (EFS) are 72% and 68%, respectively. For patients proceeding to SCT, the 4-year OS and EFS are 79% and 73%, respectively. All patients who received allografts are alive without disease at 38-141 months since diagnosis. For patients who received autografts, the 4-year EFS is 69%. Bone marrow involvement was a significant prognostic factor predicting for a worse survival (P = 0.02).

CONCLUSION

A treatment strategy for adults with chemosensitive T-LBL that includes planned consolidation with SCT in first response produces favorable long-term outcome.

Exaggerated vasomotor response to ANG II in rats with fetal programming of hypertension associated with exposure to a low-protein diet during gestation

The renin-angiotensin system plays a key role in the initiation and maintenance of elevated blood pressure associated with altered intrauterine milieu. The current studies were undertaken to verify whether vascular response to ANG II is increased in adult offspring of low-protein fed dams (LP) compared with control (CTRL) and if so, to examine underlying mechanism(s). ANG II-induced contraction of carotid rings was increased in LP (Emax, the maximum asymptote of the curve, relative to maximal response to KCl 80 mM: 230 ± 3% LP vs. 201 ± 2% CTRL, P < 0.05). In both groups, contraction to ANG II was mediated solely by AT1R. Responses to thromboxane A2 analog U-46619 and to KCl 80 mM under step increases in tension were similar between groups. Endothelium depletion enhanced contraction to ANG II in both groups, more so in LP. Blockade of endothelin formation had no effect on response to ANG II, and ANG-(1–7) did not elicit vasomotor response in either group. Superoxide dismutase (SOD) analog Tempol normalized LP without modifying CTRL response to ANG II. Basal levels of superoxide (aortic segments, lucigenin-enhanced chemiluminescence and fluorescent dye hydroethidine) were higher in LP. ANG II further increased superoxide production in LP only, and this was inhibited by coincubation with diphenylene iodonium or apocynin (inhibitor of NADPH oxidase complex). AT1R expression in carotid arteries was increased in LP, whereas SOD expression was unchanged. In conclusion, vasoconstriction to ANG II is exaggerated in this model of developmental programming of hypertension, secondary to enhanced vascular production of superoxide anion by NADPH oxidase with concomitant increase of AT1R expression.

Shifting to outpatient management of acute myeloid leukemia: a prospective experience

BACKGROUND

We assessed the feasibility of outpatient chemotherapy and supportive care in patients with acute myeloid leukemia (AML).

PATIENTS AND METHODS

All patients receiving curative intent chemotherapy between 09/01 and 10/02 and meeting our criteria received supportive care post induction chemotherapy as well as their entire consolidation chemotherapy cycles as outpatients. Patients received antimicrobial prophylaxis; those developing episodes of fever and not meeting the criteria for admission were treated with outpatient intravenous antibiotics.

RESULTS

Seventy-one cycles of induction chemotherapy were administered for newly diagnosed or relapsed AML. In 25 cycles the patient was discharged post chemotherapy prior to count recovery. Of these, 14 patients developed one or more febrile episodes as an outpatient and nine (36%) required readmission to hospital. Sixty-seven consolidation cycles were given on an outpatient basis. In 39 cycles there was one or more febrile episodes and in 14 (21%) admission was required. Infections were documented in four cases during induction and in 27 during consolidation. There were no treatment-related deaths.

CONCLUSIONS

Outpatient management of AML is safe and feasible using the strategies outlined in this report.

Myeloablative allografting for chronic lymphocytic leukemia: evidence for a potent graft-versus-leukemia effect associated with graft-versus-host disease

In all, 30 patients with CLL proceeded to myeloablative allogeneic BMT using related (n=20, 67%) or unrelated (n=10) donors, at the Princess Margaret Hospital (Toronto) (n=20) or the Leukemia/BMT Program of BC (Vancouver) (n=10), from 1989 to 2001. Median (range) interval from diagnosis to BMT was 4.8 (0.3-13) years, median number of prior therapies was three and median age 48 years. The preparative regimen included total body irradiation in 15 (50%). In all, 14 of 30 patients (47%) are alive, with median (range) follow up of 4.3 (2.4-10.5) years. All are in complete remission, two following therapy for post-BMT progression. Actuarial overall (OS) and event-free survival (EFS) at 5 years is 39% (OS 48% for related donor and 20% for unrelated donor BMT); cumulative incidence of nonrelapse mortality (NRM) and relapse is 47 and 19%, respectively. Both acute (RR=0.008, P=0.01) and chronic (RR=0.006, P=0.02) Graft-versus-host disease (GVHD) were associated with markedly decreased risk of relapse. Patients receiving grafts from unrelated donors had increased NRM (RR=3.6, P=0.02) and decreased OS (RR of death=3.4, P=0.002). Allogeneic BMT has resulted in long-term EFS in approximately 40% of patients with CLL. There is evidence for a strong graft-versus-leukemia effect associated with acute and chronic GVHD, resulting in near complete protection from relapse.

Characteristics and outcome of patients developing endocarditis following hematopoietic stem cell transplantation

Endocarditis is an uncommon complication of hematopoietic stem cell transplantation (HSCT). A retrospective review of 1547 patients who underwent HSCT in Vancouver between January 1986 and December 2001 was performed. In all, 20 cases of endocarditis were identified (1.3% of all patients) with nine patients having received cryopreserved autologous stem cells, six stem cells from a histocompatible sibling and five patients stem cells from an unrelated donor. Five patients had endocarditis diagnosed while alive, a median of 6 months post-HSCT, by transthoracic (four patients) or transesophageal (one patient) echocardiography. The remaining 15 cases of endocarditis were only identified post mortem. The mitral valve was the most frequently involved (10 patients) followed by the aortic valve (six patients); multivalvular disease was noted in five patients. Of the 11 affected allogeneic HSCT patients, 10 had previously developed acute graft-versus-host disease (GVHD). Causative organisms were identified in 11 patients, while nine additional cases were felt to be thrombotic in origin. Of the 20 patients, 19 died with the sole survivor alive 10 years following an aortic valve replacement. Endocarditis is an uncommon complication of HSCT usually involving the cardiac valves on the left side of the heart and is associated with a high mortality rate.

Second malignancy following high-dose therapy and autologous stem cell transplantation: incidence and risk factor analysis

To establish incidence and risk factors for development of second malignant neoplasms after high-dose chemo/radiotherapy (HDT) and autologous hematopoietic stem cell transplantation (AHSCT), the case files of 800 consecutive patients who underwent AHSCT at our institution between June 1982 and December 2000 were reviewed. In all, 26 patients developed 29 second malignancies (nine myelodysplastic syndrome (MDS)/acute myelogenous leukemia (AML), 16 solid tumors and four lymphoproliferative disorders (LPDs)) for a 15-year cumulative incidence of 11% (95% confidence interval (CI), 5-18%). These second tumors occurred at a median of 68 (range 1.5-177) months following AHSCT. The relative risk (RR) compared to the general population of developing a second malignancy following AHSCT was 3.3 (CI 2.2-4.7) P<0.001. The RR of developing MDS/AML, LPD and a solid tumor was 47.2 (CI 21.5-89.5) P<0.001, 8.1 (2.2-20.7) P=0.002 and 1.98 (1.1-3.2) P=0.009, respectively. In multivariate analysis, age >or=35 years at the time of AHSCT (P=0.001) and an interval from diagnosis to AHSCT >or=36 months (P=0.03) were associated with a greater risk of developing a second malignancy. Patients who have undergone HDT and AHSCT are at significant risk for developing a second malignancy and should receive indefinite follow-up.

Acute myelogenous leukemia complicated by acute necrotizing ulcerative gingivitis due to Aspergillus terreus

Infections caused by Aspergillus terreus are rare but have been associated with a poor outcome in immunocompromised patients due to frequent resistance to conventional antifungal therapy. This report describes a case of a woman who developed acute necrotizing ulcerative gingivitis (ANUG) due to A. terreus during induction chemotherapy for acute myelogenous leukemia. She initially failed to respond to treatment with amphotericin B but the infection resolved following the introduction of oral itraconazole. Opportunistic infections caused by A. terreus are an emerging problem and can be associated with a high mortality rate. Early microbiological diagnosis is critical since resistance to amphotericin B is likely and itraconazole appears to be an effective treatment for this infection.

Fulminant tumour lysis syndrome in acute myelogenous leukaemia with inv(16)(p13;q22)

Tumour lysis syndrome (TLS) is caused by rapid breakdown of malignant cells resulting in electrolyte disturbances and acute renal failure. TLS has rarely been described in patients with acute myelogenous leukaemia (AML). Between November 1997 and July 2001, 114 consecutive adult AML patients aged <60 yr received induction chemotherapy consisting of cytosine arabinoside 1.5 g m(-2) q 12 h x 12 doses and daunorubicin 45 mg m(-2) d(-1) x 3 doses. During induction chemotherapy (CT), seven patients (6.1%, 95% CI 2.5-12.2) developed fulminant TLS, resulting in acute renal failure; five of these seven patients had inversion of chromosome 16 [inv(16)(p13;q22)], and one patient had a biological equivalent [t(16,16)(p13;q22)]. Four of the TLS patients underwent leukapheresis for a presenting white blood cell (WBC) count > 100 x 10(9) L(-1) prior to commencing chemotherapy, and six patients subsequently required haemodialysis for a median of 2 (range 1-8) wk. One TLS patient died of intracerebral hemorrhage on day 10 and another patient of multiorgan failure on day 17. Of the other five patients, all entered a complete remission (CR) and recovered normal renal function. Four patients remain in continuous CR [median follow-up 20 (range 12-25) months]. One patient relapsed at 12 months and again developed TLS on re-induction. In univariate analysis, TLS patients were more likely to have an elevated presentation and pre-chemotherapy WBC counts, elevated serum creatinine, and uric acid levels at presentation, as well as an inv(16). In multivariate analysis, only serum creatinine and inv(16) remained statistically significant (P < 0.001 for each). Patients with an inv(16) are a unique AML subgroup at high risk for fulminant TLS.

Photoprotection of solutions of parenteral nutrition decreases the infused load as well as the urinary excretion of peroxides in premature infants

Light exposure and multivitamins are contributing factors to the generation of peroxides in solutions of parenteral nutrition. This article verifies if peroxides infused with parenteral nutrition are of biological significance in neonates. The mechanisms responsible for the generation of peroxides in total parenteral nutrition solutions are reviewed. The consequences of infused peroxides on an index of oxidant stress and on levels of a central antioxidant are evaluated in an animal model. The effect of photoprotection of parenteral nutrition on a biological marker of redox imbalance is evaluated in the urine of premature infants. Parenteral multivitamins produce a drop in glutathione and an oxidant stress similar to peroxides in the lungs of newborn guinea pigs. Infused peroxides elicited an increased urinary peroxide excretion in infants receiving parenteral nutrition exposed to light. Photoprotection reduced levels of infused and excreted peroxides. The results suggest that peroxides infused with total parenteral nutrition are not fully quenched by premature infants.

Parenteral multivitamin supplementation induces both oxidant and antioxidant responses in the liver of newborn guinea pigs

BACKGROUND

The multivitamin solution is a major component of photo-induced generation of peroxides in parenteral nutrition. The aim of this study was to determine whether the parenteral multivitamin preparation induces in the liver a peroxide-induced oxidant challenge or an antioxidant protection associated with the antiradical components of the solution.

METHODS

Newborn guinea pigs were infused with dextrose supplemented with peroxides (250 micromol/L H2O2 or 350 micromol/L tert-butylhydroperoxide) or with a multivitamin preparation (MVP, 1% vol/vol). After 4 days, total glutathione and a free radical-sensitive eicosanoid marker (prostaglandin I2 [PGI2]/total prostaglandins) were measured in livers.

RESULTS

There was a significant decrease in the PGI2/total prostaglandin ratio (mean +/- SEM) [dextrose: 0.068 +/- 0.007 vs. (dextrose + H2O2: 0.048 +/- 0.001, dextrose + TBH: 0.043 +/- 0.001)] and glutathione concentrations decreased [dextrose: 55 +/- 7 vs. (dextrose + H2O2: 37 +/- 7, dextrose + TBH: 18 +/- 7 nmol/mg protein)] after infusion of peroxides. Despite the peroxide load in the multivitamin solution, it did not alter the measured variables as prostanoid ratio remained at control concentrations (dextrose: 0.066 +/- 0.008 vs. dextrose + MVP: 0.065 +/- 0.006), as did glutathione levels (dextrose: 52 +/- 6 vs. dextrose + MVP: 45 +/- 7 nmol/mg prot).

CONCLUSION

In the liver of guinea pig pups, infused peroxides cause oxidation of membrane-derived prostanoids. The decrease in glutathione in response to administration of peroxides suggests consumption rather than a response to a free radical attack. Despite the oxidant load associated with peroxides generated in MVP, the multivitamin preparation protected membranes as the prostanoid ratio, and glutathione levels remained at control levels.

Peroxide-like oxidant response in lungs of newborn guinea pigs following the parenteral infusion of a multivitamin preparation

The multivitamin solution is a major component responsible for the photo-induced generation of peroxides in parenteral nutrition. The lung is a target of oxidant injury; however, the specific role of infused peroxides is unknown. The aim of this study was to determine if parenteral multivitamins induce in the lung an oxidant challenge similar to that of peroxides. Newborn guinea pigs were infused with dextrose plus relevant concentrations of H(2)O(2) (0,250,500 microM) or multivitamins (0,1%), as well as parenteral nutrition supplemented with multivitamins (0,1%). After 4 days, total glutathione, glutathione-related enzymes, and oxidant-sensitive eicosanoids were measured in the lungs. Peroxides as well as multivitamins led to a significant decrease in glutathione and the activity of glutathione synthase, indicating that infused peroxides were not entirely transformed into free radicals, which would have stimulated glutathione synthesis. The multivitamin solution induced a response in oxidant-sensitive eicosanoids similar to the response to peroxides, suggesting an oxidant stress that was not alleviated by the antiradical properties of its components. The effects on prostaglandins occurred independently from the stimulation in glutathione levels induced by parenteral nutrition. The multivitamin solution carries an oxidant load and causes effects similar to those of peroxides in the lungs of newborn guinea pigs.

Increased urinary peroxides in newborn infants receiving parenteral nutrition exposed to light

OBJECTIVES

To determine whether peroxide loads infused with total parenteral nutrition (TPN) are fully quenched by premature infants.

STUDY DESIGN

After baseline urine peroxide levels were established, the effect of various parenteral regimens was correlated with urinary peroxide levels in 64 newborn infants </=32 weeks' gestation. This correlation was achieved with the properties of light and of various parenteral nutrient admixtures on the generation of peroxides. Peroxides were measured by the ferrous oxidation of xylenol orange.

RESULTS

The level of urinary peroxides measured for infants given a fat-free TPN regimen unprotected from light (74.5 +/- 15.3 micromol/L) was similar to levels found in infants given a lipid-containing regimen (88.1 +/- 10.3 micromol/L). When photoprotected, the fat-free alimentation was associated with peroxide levels (28.8 +/- 2.8 micromol/L) similar to those measured before TPN (27.6 +/- 4.1 micromol/L).

CONCLUSIONS

Because urine peroxide levels are changed by various nutritional procedures, antioxidant systems of premature infants are unable to fully quench the oxidant load associated with TPN.

Contribution of multivitamins, air, and light in the generation of peroxides in adult and neonatal parenteral nutrition solutions

OBJECTIVE

To compare the concentrations of peroxides between adult and neonatal total parenteral nutrition (TPN) solutions in response to protection against inducers of peroxidation such as multivitamins and exposure to light or air.

METHODS

Peroxide concentrations were measured in freshly prepared adult and neonatal solutions of fat-free TPN in four settings: with or without an air inlet, and protected or unprotected from ambient light. An oxygen washout was performed by exposing a fat-free neonatal TPN solution to a continuous flow of nitrogen.

RESULTS

Globally, light was the main inducer of peroxides in adult and neonatal solutions. However, in adult solutions the concentration of peroxides remained <15 micromol/L, while in neonatal solutions the peroxide concentration was as high as 300 micromol/L in ambient light. Although the oxygen washout did prevent the generation of peroxides, avoiding air inlet was not as effective as was photoprotection in decreasing the important peroxide load in the neonatal TPN solution.

CONCLUSIONS

The higher concentration of peroxides found in neonatal solutions compared with adult solutions is explained by the differences in nutrient composition between the two solutions. Contamination of parenteral solutions by air during compounding accounts for the photoinduced generation of peroxides in TPN solutions. It is more convenient to protect TPN solutions from light exposure after the admixture of the multivitamin solution than to avoid contact with oxygen.

Survival of guinea pig pups in hyperoxia is improved by enhanced nutritional substrate availability for glutathione production

The imbalance between high oxidant loads and immature antioxidant defenses is associated with long-term complications of prematurity. Glutathione is a central element among the antioxidants. Depletion of pulmonary glutathione accelerates the development of oxygen-induced lung injury in neonatal animal models. After the observation that newborn infants exposed to oxygen have low glutathione levels, a study was designed to test the hypothesis that in neonates from a species susceptible to oxygen toxicity, the lethal effect of hyperoxia is related to a low availability of substrates for glutathione production rather than an impairment in synthetic activity. One-day-old guinea pigs, randomly assigned to room air or oxygen (>95%), were fed by their mothers (n = 16) or i.v. by dextrose (n = 14) or by total parenteral nutrition (TPN, n = 20). After 3 d, glutathione and activities of enzymes involved in maintaining intracellular glutathione levels were determined in lungs and liver. The lethal effect of oxygen (p < 0.05) observed in animals without TPN was not related to glutathione depletion, as oxygen induced a 33% increase in lung glutathione, positively correlated (r2 = 0.35) with enhanced synthesis. With TPN, the animals were protected against the lethal effects of hyperoxia and lung glutathione increased by 67% in oxygen. The results suggest that the glutathione demand by the lungs in the presence of an oxidant stimulus was met by the increased (p < 0.001) hepatic production supported by TPN. Under hyperoxic conditions, early nutritional support is of vital importance.

N-acetylcysteine in pig liver transplantation from non-heart-beating donors

Lipid peroxidation due to oxygen free radicals (OFR) seems to play a major role in loss of liver graft viability after warm ischemia, preservation, and transplantation. N-acetylcysteine (NAC) is an antioxidant that has a direct effect on OFR, and is also a glutathione precursor, another antioxidant. This study was designed to evaluate the efficacy of NAC in preventing ischemia-reperfusion damage of liver grafts harvested from non-heart-beating donors. Liver transplantation was performed on pigs divided into five groups: group 1 (control group; n=5) received livers from heart-beating donors; livers were subjected to 30 min of warm ischemia in groups 2 (n=3, no NAC) and group 3 (n=3; NAC treatment); warm ischemia time lasted 60 min in groups 4 (n=4; no NAC) and 5 (n=5; NAC treatment). Studied parameters included graft survival for more than 3 days, aspartate aminotransferase plasma levels, liver histology, and hepatic total glutathione concentrations. Graft survival was 100% in groups 1, 2, and 3, 0% in group 4, and 20% in group 5. NAC treatment did not influence initial mean aspartate aminotransferase release which was greater in warm ischemic livers than in controls. NAC treatment had no effect on liver hepatic total glutathione after reperfusion of animals receiving warm ischemic grants. Finally, no effect on liver histology was observed with NAC treatment. Our study suggests that in liver transplantation from non-heart-beating donors, NAC has no effect in both graft viability and lipid peroxidation. The role of OFR in primary dysfunction of transplanted warm ischemic livers remains controversial.

Protecting solutions of parenteral nutrition from peroxidation

BACKGROUND

Light exposure induces the generation of peroxides in solutions of total parenteral nutrition (TPN). Peroxide toxicity has been documented in cell, in tissue, and in isolated organs. To decrease the infused peroxide load and to protect the quality of the parenteral nutrients, we tested the photoprotective properties of different infusion sets.

METHODS

Solutions of fat-free TPN and all-in-one total nutrient admixture (TNA) were run through sets of bags (clear and covered) and tubings (clear and colored: black, orange, and yellow) offering different levels of protection against light. Peroxide levels were determined by ferrous oxidation of xylenol orange, thiol functions by the 5,5,-dithiobis(2-nitrobenzoic acid) technique, and absorbance of tubings by spectroscopy.

RESULTS

Protection of only the bag had little effect on peroxide generation. In fat-free TPN solutions kept in covered bags, peroxide concentrations were 1.5 to 2 times higher when run through clear compared with colored tubings. When exposed to phototherapy or in the presence of lipids, peroxides were two to three times higher with the clear compared with the black tubing; meanwhile, orange and yellow tubings offered varying levels of protection related to their light-absorbing properties. Colored tubings offered a greater protection against the disappearance of thiol functions.

CONCLUSIONS

Covering bags and using orange and yellow tubings may be a practical solution to reduce infused peroxide loads from about 400 to 100 microM. This is especially relevant in patients with an immature or a compromised antioxidant capacity or when phototherapy or preparations of TNA are used.

Glutathione synthetic activity in the lungs in newborn guinea pigs

Depletion of glutathione, a key antioxidant, accelerates lung injury. Glutathione concentrations are reduced significantly in premature infants with respiratory distress syndrome, leaving them at greater risk of bronchopulmonary dysplasia. A study was designed to verify if the increased glutathione synthetic activity observed in oxygen-dependent and ventilated newborn infants was caused by their postsurgical state. Our objective was to evaluate the role of a general surgical procedure as a factor affecting lung glutathione. One-day-old guinea pig pups, a well characterized animal model for the study of neonatal lung disease, were divided between those undergoing a standardized surgical procedure and those that did not. The pups were fed by their mother. After 4 days the lungs were sampled to determine total glutathione content, activities of gamma-glutamyltranspeptidase, glutathione peroxidase, and reductase as well as the glutathione synthetic activity. The surgical procedure was associated with a specific stimulatory effect limited to glutathione synthetic activity (p < 0.02) leading to an increased (p < 0.02) pulmonary glutathione content. Glutathione concentration was significantly correlated (r2 = 0.67) with the synthetic activity. We concluded that in this animal model an invasive procedure such as a general surgical procedure affects lung glutathione metabolism in a fashion similar to that of hyperoxia. In the lungs, the synthetic activity is a stronger determinant of glutathione concentrations than the activities of the other enzymes involved in maintaining glutathione levels.

[Intrahepatic glutathione and oxidative stress in liver transplantation in the pig]

OBJECT

To determine the loss of endogenous GSH from livers cold-stored and reperfused, using a model of liver transplantation in the pig.

MATERIAL AND METHODS

Four female Yorkshire pigs weighing 19 to 40 kg received a liver allograft. Donor livers were cold-stored in the UW solution. Mean cold ischemic time was 6.5 hours. Malondialdehyde (MDA) levels were used as an index of oxidative stress. MDA plasma levels were measured following recipient laparotomy (H0), immediately (H1), and 90 minutes after liver reperfusion (H2). MDA and GSH levels in liver were measured following donor laparotomy (T0), at the end of cold ischemic period (T1), and at 90 minutes following liver reperfusion (T2).

RESULTS

Three animals survived. MDA liver levels decreased of 44% between T0 and T1, then increased to 92% at T2. In contrast, in plasma, graft reperfusion was associated with an increase of MDA to 140% of the baseline values which reached 188% at H2. Intrahepatic GSH levels decreased of 49% at T1, then to 72% at T2.

CONCLUSION

our study suggests that in liver transplantation: (1) Hepatic GSH is depleted to 49% during cold-storage, and an additional 23% is lost after reperfusion; (2) GSH contained in the UW solution does not prevent the loss of hepatocellular glutathione during preservation and reperfusion; (3) after short periods of cold ichemia, endogenous hepatic GSH may protect against oxydative stress in the transplanted liver.

Paradoxical role of ascorbic acid and riboflavin in solutions of total parenteral nutrition: implication in photoinduced peroxide generation

In the presence of light, a multivitamin preparation is the main source of peroxides in solutions of total parenteral nutrition (TPN). This preparation contains two photosensitive products, 5'-phosphate flavin mononucleotide (FMN) and polysorbates (PS), as well as electron donors such as ascorbate (AH). We hypothesized that the admixture of FMN or PS with electron donors generates peroxides in TPN and alters the quality of nutrients. Using xylenol orange, peroxide concentrations were measured in solutions containing AH, FMN, and/or PS in water, a dextrose solution, an amino acid preparation, and a lipid emulsion. Thiol functions were evaluated by reduction of 5,5-dithiobis(2-nitrobenzoic acid) in the amino acid preparation. After 24-h light exposure, dextrose solutions with admixtures of AH + FMN or AH + FMN + PS generated peroxides at concentrations similar to those observed in a 1% multivitamin solution, and over three times higher than those observed with FMN, PS, or AH alone. However, in the presence of amino acids, FMN alone induced a generation of peroxides comparable to that observed with FMN + AH. In the lipid emulsion, peroxides increased over 3-fold in the presence of FMN or FMN + AH. The addition of catalase suggested that lipid peroxides and H2O2 were produced, and the loss of thiol function suggested that an oxidation of amino acids occurred. When exposed to light, FMN induces reactions with amino acids, polyunsaturated fatty acids, and even AH, altering the quality of nutrients. Paradoxically, AH without FMN has a protective effect on peroxide generation in TPN.

Development of glutathione synthesis and gamma-glutamyltranspeptidase activities in tissues from newborn infants

Following the observation that the level of glutathione in leukocytes from human newborn infants was lower in preterm and in male infants, a study was designed to document the level of activities of glutathione synthesis and gamma-glutamyltranspeptidase during the development of preterm and term newborn infants. Measurements were performed in leukocytes from tracheal aspirates of oxygen dependent infants, and in leukocytes from cord blood. Contrary to the common belief concerning the development of antioxidant activity, the biosynthesis of glutathione was active in leukocytes from preterm infants; and by two days of life the activity of gamma-glutamyltranspeptidase reached 3 times the level of that seen in cord blood. Our results suggest that the maturity of these enzymes was not the limiting step in maintaining cellular glutathione levels. This represents new information concerning the maturation of a central antioxidant in tissue derived from preterm and term human newborn infants at risk of oxidant stress. This implies that sources of cysteine crossing freely the cellular membrane could be used by tissues of term and preterm infants to produce glutathione.

Bound iron admixture prevents the spontaneous generation of peroxides in total parenteral nutrition solutions

BACKGROUND

Parenteral administration of iron is a matter of controversy because it is feared that it could contribute to oxidative reactions. The aim of this study was to verify if irondextran participates in the redox reactions occurring in total parenteral nutrition (TPN) solutions.

METHODS

Irondextran was compared with different forms of iron in the interaction with peroxides. Hydroperoxide levels were measured by a colorimetric technique in TPN solutions, in presence of varying sources (FeCl2, FeSO4, irondextran, iron sorbitol) and concentrations (0-0.8 mM) of iron. The consumption and inhibition of peroxide generation were tested by analyzing the effect of iron on different sources of peroxides (H2O2, tert-butyl and cumen hydroperoxide). The free radicals produced under conditions of a Fenton-like reaction were measured by the oxidation of scopoletin. And the proportion of Fe3+ freed by both bound-iron sources was counted by measuring the masking effect on the thiol function of cysteine.

RESULTS

Free-iron admixture to parenteral nutrition induces the formation of free radicals, whereas sources of bound-iron inhibit the generation of peroxides in parenteral nutrition without implying a Fenton-like reaction.

CONCLUSION

For patients requiring iron supplementation, bound-iron should be added during the preparation of TPN solutions, because it protects against the spontaneous generation of peroxides.

Admixture of a multivitamin preparation to parenteral nutrition: the major contributor to in vitro generation of peroxides

BACKGROUND

Peroxides have been reported to contaminate lipid emulsions and amino acid solutions used in total parenteral nutrition (TPN). This is particularly disturbing in newborn infants who are prone to several diseases related to immature defense mechanisms against oxidative challenges. It is not clear whether the antioxidants in multivitamins help protect parenteral nutrients against the hazards of oxidation.

OBJECTIVE

To evaluate the role of a multivitamin preparation (MVI) on the actual peroxide load received by patients on TPN.

METHODOLOGY

The generation of peroxides in parenteral nutrition was tested first using test solutions. We compared the relative contribution of commercially available amino acid solutions, a lipid emulsion, and MVI on the level of peroxides in clinically relevant TPN solutions. Second, we measured the level of peroxides actually infused at the bedside. In both circumstances, the effects of time and light exposure were isolated. The level of peroxides was determined by a colorimetric technique and expressed as microM equivalents tert-butyl hydroperoxide (microM = TBH).

RESULTS

Even when protected from light, the addition of MVI produced a 10-fold increase in peroxides (mean +/- SEM, n = 3, 19 +/- 4 to 189 +/- 8 microM = TBH at 4 h) in the fat-free TPN solution and a fourfold increase (64 +/- 6 to 244 +/- 8 microM = TBH at 4 h) in the lipid-containing TPN solution. A dose-response relationship was found between the concentration of MVI and peroxide levels. The effect of light was the strongest in the presence of multivitamins. The amino acid solutions had a relative inhibitory effect on the generation of peroxides by MVI, which varied (from 54 +/- 1% to 72 +/- 1%) all according to the amino acid blend. In parenterally fed premature infants, protecting the intravenous set from light decreased the load of infused peroxides (146 +/- 15 vs 215 +/- 24 microM = TBH).

CONCLUSIONS

The lipid emulsion had a significant but minor additive effect compared with the multivitamin preparation, which was the major contributor to the generation of peroxides. Protection from photooxidation is not sufficient to prevent peroxidation of TPN solutions. Contrary to what one would expect, increasing the concentration of MVI will lead to a greater generation of peroxides, suggesting that the essential antioxidants in MVI do not have antiperoxide properties.

Gender and maturation affect glutathione status in human neonatal tissues

Gender and maturation affect glutathione status in human neonatal tissues. The objective was to verify if human tissues derived from baby girls had a greater ability then tissues derived from males to stimulate the glutathione-reductase, when faced with an oxidative challenge. In vitro, the effect of a calibrated oxidative challenge was studied in endothelial cells. In vivo, the effect of a clinically relevant oxidative challenge was studied in cells from tracheal aspirates derived from oxygen-dependent newborn infants. In endothelial cells, the oxidant tert-butylhydroperoxide had a stimulating effect on GSSG-R activity in cells derived from females. The peroxide produced a time, concentration and gender-dependent cytotoxicity, with female-derived cells exhibiting a better viability. In vivo, the intracellular total glutathione content was higher in female-derived cells and in cells from more mature babies; postnatal age and gestational age had a positive effect on the activity of GSSG-R. Oxygen (FiO2 > or = 0.3) was associated with a lower activity of GSSG-R in boys, early in life. Considering that glutathione is a central element in the antioxidant defense, these results suggest that specific tissues derived from the baby girl are potentially better protected against an oxidative stress than those derived from the boy.

Influence of bilirubin on the antioxidant capacity of plasma in newborn infants

In vitro, bilirubin is a strong antioxidant, but in vivo its capacity to act as a scavenger of toxic oxygen radicals remains poorly documented. The aim of this study was to evaluate of bilirubin had antioxidant properties in jaundiced infants. The antioxidant capacity of neonatal plasma was measured in Trolox equivalents (TEAC, mmol/l) and correlated in vitro with plasma bilirubin concentrations (r2 = 0.99). Plasma TEAC was compared before and after exchange transfusions for neonatal hyperbilirubinemia (250-435 mumol/l). The antioxidant properties of the paired blood samples before and after exchange transfusions (TEAC: 1.67 +/- 0.12 vs. 1.37 +/- 0.09 mmol/l, n = 11) varied in proportion to the serum bilirubin levels. The changes in other antioxidants were not large enough to account for the magnitude of change in antioxidant capacity. Therefore, in vivo, the plasma antioxidant capacity of jaundiced newborn infants is related to the level of bilirubin.

The increase in vasomotor tone induced by a parenteral lipid emulsion is linked to an inhibition of prostacyclin production

The aim of the study was to verify whether the infusion of a lipid emulsion causes a rise in vascular pressure related to an imbalance in the production of vasoconstricting and vasodilatating eicosanoids. Segments of umbilical veins were perfused with and without 1.5 microM indomethacin (cyclooxygenase inhibitor) in solutions differing only in their lipid content (control vs. lipid). The lipid-induced higher pressure (p < 0.05) was associated with an inhibition (p < 0.05) in the output of the vasodilatator PGI2, and an increase (p < 0.01) in the production of the vasoconstrictor PGF2 alpha. Indomethacin abolished differences in pressure, but produced a rise (p < 0.01) in vascular tone of both the control and lipid-containing solutions by inhibiting PGI2 synthesis. Prostacyclin was the only eicosanoid significantly correlated (p < 0.01) to vascular tone. The lipid emulsion was therefore linked to the inhibition of the conversion of PGH2 to PGI2. The ensuing greater PGH2 availability would result in vivo, in the increased synthesis of vasoconstricting eicosanoids. The lipid-containing solution produced vasoactive responses similar to those reported with tert-butyl hydroperoxide, suggesting that hydroperoxides contaminating commonly used lipid emulsions could be causing a prostanoid-dependent vasoconstriction.

Antiperoxide activity of sodium metabisulfite. A double-edged sword

Sulfites are chemical substances that are used widely in the pharmaceutical industry to reduce or prevent oxidation. Sodium metabisulfite (Na2S2O5) is still present in several parenteral amino acid solutions. Since intravenous lipid emulsions are contaminated by hydroperoxides, we evaluated whether metabisulfite had an antioxidant activity against hydroperoxides. In vitro, Na2S2O5 inhibited the oxidant activity of H2O2, tert-butyl-, and cumene hydroperoxides. The antioxidant capacity of metabisulfite was supported in vivo by the lower (P < 0.01) excretion of malondialdehyde, a stable end product of lipid peroxidation, in babies receiving metabisulfite in their parenteral nutrition. However, for concentrations outside the range found in solutions for parenteral nutrition, the reduction of hydroperoxides by Na2S2O5 could transform this compound into an oxidant, like a sulfite radical. It is suggested that metabisulfite has antiperoxide properties that, under specific conditions, contribute to the generation of toxic oxidants.

Gender-related response to a tert-butyl hydroperoxide-induced oxidation in human neonatal tissue

Reports of gender-related differences in the activity of enzymes involved in the metabolism of intracellular antioxidants, led us to verify whether the prostaglandin response to tert-butyl hydroperoxide (TBH) differed according to the sex of infants. Segments of human umbilical veins were perfused in the presence or absence of TBH (0.25 mmol/l, and 1.0 mmol/l). Because TBH is quenched in the cell by glutathione peroxidase, total glutathione concentrations and production of glutathione-dependent prostaglandins (PGE2 and PGF2 alpha) as well as membrane-derived eicosanoids (PGI2 and thromboxane) were measured in the eluate. In veins from boys, TBH induced a sustained response for glutathione only, which was increased (p < 0.05). In female-derived tissue, the hydroperoxide induced a different response according to the dose of TBH. At 0.25 mmol/l, a drop (p < 0.005) in PGF2 alpha was associated with a rise (p < 0.001) in thromboxane. At 1.0 mmol/l, TBH had an opposite effect--there was a rise (p < 0.01) in PGE2 and PGI2. The prostaglandin concentration were not proportional to the oxidative stimulus, suggesting a critical level of TBH at which the oxidative state differs in tissues derived from boys or girls.

Biologic effects of parenteral bisulfite on human vascular tissue

Antioxidant properties of bisulfite are used to stabilize parenteral amino acid solutions. After reports of adverse reactions to dietary sulfites, we evaluated whether the infusion of bisulfite had biologic effects on human vascular tissue. Because an endothelial oxidative injury can affect mediators of vasoreactivity, vascular pressure and prostaglandin production were studied in an intact human vein model infused with clinically relevant amino acid solutions differing only by their metabisulfite content (0 versus 300 mg/L). The amino acid solution containing bisulfite presented higher venous pressure (p < 0.01) and prostaglandin production (6-keto-prostaglandin F1 alpha, p < 0.01; and prostaglandin E2, p < 0.05). A hydroxyl radical-generating system added to the solutions did not modify the pressure readings, but it resulted in an overall decrease in prostacyclin production (p < 0.05). Despite this known inhibitory effect on oxidative challenge on prostaglandin I2 production, prostaglandins remained higher in the presence of bisulfite. The results suggest that the effect of bisulfite takes place before prostaglandin H2 synthesis in the eicosanoid cascade, whereas the oxidative challenge affects specifically the synthesis of prostaglandin I2, after prostaglandin H2, indicating that there is no interaction between bisulfite and the hydroxyl generating system. Bisulfite has local vascular effects on endothelial mediators, separate from its antioxidant properties.

Total parenteral nutrition in the newborn infant: energy substrates and respiratory gas exchange

The hypothesis that a high-fat parenteral regimen was beneficial for respiratory gas exchanges, in comparison with a high-glucose regimen, was tested in a paired crossover design. Ten parenterally fed newborn infants with no respiratory problems received two 5-day isoenergetic and isonitrogenous regimens that differed in their nonprotein source of energy; the level of fat intake (low fat (LF) 1 gm.kg-1.day-1; high fat (HF) 3 gm.kg-1.day-1) varied inversely with that of glucose. Continuous transcutaneous PO2 (tcPO2) and PCO2 (tcPCO2), respiratory gas exchange (indirect calorimetry), and plasma arachidonate metabolites were measured at the end of each regimen. Oxygen consumption and resting energy expenditure were not affected by modification of the source of energy. However, carbon dioxide production (VCO2) was higher during LF than during HF (6.9 +/- 0.2 vs 6.2 +/- 0.1 ml.kg-1.min-1; p less than 0.01), as was the respiratory quotient (1.08 +/- 0.02 vs 0.96 +/- 0.02; p less than 0.001). Despite the differences in VCO2, the tcPCO2 was not affected, suggesting adequate pulmonary compensation during LF, as documented by the higher minute ventilation (160 +/- 7 vs 142 +/- 5 ml.kg-1.min-1; p less than 0.01). The lower tcPO2 during the HF regimen (73.8 +/- 2.8 vs 68.8 +/- 2.6 mm Hg; p less than 0.015) indicated a disturbance at the alveolocapillary level induced by the lipid emulsion. No differences were found in circulating levels of prostaglandins and thromboxanes. The substitution of glucose for lipid did not modify fat storage (2.1 +/- 0.3 vs 2.1 +/- 0.3 gm.kg-1.day-1). We conclude that the supposed beneficial effect of a fat emulsion on respiratory gas exchange is questionable.

Effects of glucocorticoids on prostaglandin formation by human amnion

The human amnion may be an important source of prostaglandins involved in the onset of human labor and therefore it is important to define the factors that regulate their formation in this tissue. In the present study we demonstrate that glucocorticoids inhibit prostaglandin production by freshly isolated amnion cells. The inhibitory action of the glucocorticoids, however, changes to a stimulatory action when the cells are maintained in primary culture for a few days. For both inhibition and stimulation, concentrations of 10(-8) M dexamethasone or greater were required to give significant effects, and estradiol and progesterone had no effect on the prostaglandin output of the cells. Epidermal growth factor (EGF), which has previously been found to stimulate prostaglandin output by confluent amnion cells, did not alter prostaglandin output of cells initially placed in culture. Furthermore, the stimulatory action of EGF and dexamethasone appeared additive. The calcium ionophore A23187 stimulated prostaglandin output in freshly isolated cells and accentuated the inhibitory effect of dexamethasone. These studies indicate that prostaglandin formation by human amnion during pregnancy could be regulated by glucocorticoids. These steroids are easily available to the amnion by way of cortisone conversion to cortisol by the maternal decidua. The results also indicate that amnion is capable of responding to glucocorticoids in both a stimulatory and inhibitory fashion and whether one or both actions are of importance in vivo is a question that is as yet unresolved.

Cyclooxygenase products formed by primary cultures of cells from human chorion laeve: influence of steroids

Cells were isolated from human chorion laeve obtained at term (38-40 weeks gestation) by elective caesarean section and were maintained in primary culture for 1 week in defined media supplemented with 10% fetal calf serum. The production of various cyclooxygenase products by the cultures was examined. Little or no prostaglandin (PG) F2 alpha, 6-keto-PGF1 alpha, thromboxane B2, or 13,14-dihydro-15-keto-PGF2 alpha was found. In contrast, the cells produced PGE2 which was low on day 0, increased during culture to a maximum on day 1 or 2, then declined to low levels. When cells were grown in the presence of media containing cortisol, dexamethasone, progesterone, and estradiol (at 10(-7) or 10(-9) M), the glucocorticoids (at 10(-7) and 10(-9) M), but not estrogen or progesterone, markedly inhibited the increase in PGE2 output. There was no difference in the protein content and thymidine incorporation of cells grown in the presence of glucocorticoids when compared with controls. This inhibitory effect was not sensitive to cycloheximide (1 microgram/mL) indicating protein synthesis may not be involved in the process. These studies indicate that PGE2 is the major prostaglandin formed by primary cultures of chorion laeve and that prostaglandin metabolism in the chorion is sensitive to glucocorticoid inhibition.

Primary culture of cells from human chorion laeve: steroid metabolism and properties of cells grown in defined media supplemented with 0.1% or 10% fetal calf serum

The purpose of this study was to develop primary cultures of human chorion laeve cells and examine certain aspects of steroid metabolism during culture. Tissues obtained by elective cesarean section at term (38-40 weeks) were dispersed with collagenase. Cells were isolated on Percoll gradients at the interface between 20% and 40% Percoll and examined in primary culture for up to 1 week. Cultures were carried out in chemically defined media supplemented with 10% or 0.1% fetal calf serum (FCS). The morphological and biochemical properties of the cells were different in the two systems. In 0.1% FCS, cells formed clumps of tissue within 16 h of plating, and there was no cell replication. In contrast, in 10% FCS, the cells formed a carpet of tissue and reached confluence after 5 days in culture, resulting in increased DNA and protein content and thymidine incorporation in the dishes. Three steroidogenic enzymes were studied during culture: alkyl steroid sulfatase, estrogen sulfatase and 3 beta-hydroxysteroid dehydrogenase. The sulfatases had higher activities in 0.1% than in 10% FCS, and their activities decreased markedly during the culture period. In contrast, 3 beta-hydroxysteroid dehydrogenase activity was higher in 10% FCS than in 0.1% FCS. Activity remained constant during the culture period in 0.1% FCS and increased in 10% FCS. In the latter system this increase resulted in the enzyme maintaining a constant specific activity during culture. These studies describe two viable systems of chorion laeve cells in primary culture, which may be valuable for studying long term and/or subtle effects on various metabolic aspects of this tissue.

Steroid metabolism by cells from human chorion laeve isolated on Percoll gradients

Collagenase-dispersed cells from human chorion laeve were examined on Percoll gradients. The 3 beta-hydroxysteroid dehydrogenase (a trophoblast marker) and steroid sulfatase activities of the cells were measured and a system was developed to isolate enriched preparations of the trophoblast cells. No cells were found to sediment at Percoll concentrations greater than 50%, and using continuous gradients of Percoll there appeared to be cells with different 3 beta-hydroxysteroid dehydrogenase (3 beta HSD): steroid sulfatase ratios sedimenting in different regions of the gradient. Cells with a high ratio were found in the denser region of the gradient. Continuous gradients provided inadequate separations of distinct populations of cells, thus to obtain a more reproducible system to isolate cells, discontinuous gradients of Percoll were studied. A discontinuous gradient composed of 5, 20, 40, and 60% Percoll was developed and three bands of cells were found sedimenting at the 20, 40 and 60% interfaces, respectively. The number and appearance of cells at the 20 and 60% interfaces varied from tissue to tissue. In contrast, the cells sedimenting at the 40% interface were less variable, a substantial number was found to be present in every tissue studied, they were similar in appearance to the trophoblast cells and had high 3 beta HSD:sulfatase ratios.

Steroid metabolism by human chorion laeve from dichorionic twin pregnancies

Certain steroid metabolic properties of chorion laeve from dichorionic twin pregnancies were examined to determine whether they were present in chorion not contaminated by decidua or serum. In the chorion situated between the two amniotic sacs and not in contact with decidua, aryl sulfatase, 3 beta-hydroxysteroid dehydrogenase, and aromatase activities were found. This indicates that these reactions are present in chorion laeve and were not previously ascribed to this tissue because of decidual contamination. Specific cortisol binding was also present in this area of chorion laeve, which excludes serum contamination. It is suggested that the specific steroid-binding protein in the membranes may be derived from the transcortin-like protein present in amniotic fluid.

Kinetic comparison of the 3 beta-hydroxysteroid dehydrogenase activity in human placenta, chorion laeve, and ovary

Recent studies from our laboratory and others have shown that Km values for steroid substrates of the 3 beta-hydroxysteroid dehydrogenase in the human placenta were in the nanomolar range compared with micromolar values previously described. The purpose of the present study was to measure the kinetic parameters of the 3 beta-hydroxysteroid dehydrogenase in other human tissues, namely the ovary and chorion laeve, and to determine whether they were similar to those of the placental enzyme. In chorion laeve microsomes the 3 beta-hydroxysteroid dehydrogenase had Km values for dehydroepiandrosterone and pregnenolone similar to those found in placenta. Microsomes from human ovaries, on the other hand, had Km values for both substrates 10- to 20-fold higher. However, the ability of various steroids to inhibit the ovarian enzyme was similar to that previously described from the placenta and the chorion laeve.

Kinetic studies on the formation of estrogens from dehydroepiandrosterone sulfate by human placental microsomes

Using microsomes isolated from term human placentae kinetic analyses of each of the enzymes involved in estrogen synthesis from dehydroepiandrosterone sulfate have been carried out and the following parameters were found: sulfatase, Michaelis-Menten constant (Km) = 16,000 +/- 5,000 nM, maximum velocity (Vm) = 2.0 +/- 0.5 nmol X min-1 X mg protein-1; 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), Km = 15 +/- 3 nM, Vm = 1.8 +/- 0.4 nmol X min-1 X mg protein-1; aromatase, Km = 14 +/- 4 nM, Vm = 0.12 +/- 0.02 nmol X min-1 X mg protein-1. From these values one can predict that, theoretically, the rate-limiting enzyme in estrogen synthesis from dehydroepiandrosterone sulfate (DS) should change from the sulfatase at low concentrations of substrate to the aromatase at higher concentrations. In order to test this hypothesis we developed a system which allowed the formation of estrogens from DS, dehydroepiandrosterone, and androstenedione to be measured and the appropriate intermediates to be isolated. The sulfatase was found to be rate limiting at concentrations of DS below 2 microM and the aromatase was found to be rate limiting at higher concentrations. These data may explain why previous perfusion studies of human placentae indicated the sulfatase was the rate-limiting enzyme in estrogen synthesis yet in vitro studies found that it was the aromatase. Steroids previously shown to inhibit the 3 beta-HSD were examined for their ability to inhibit the formation of estrogens from DS. Although 3 beta-HSD activity was markedly inhibited this had little effect on the overall conversion of DS to estrogens, until high concentrations of inhibitors were used. The data also underline the importance of studying enzyme systems rather than single enzymes when studying steroid synthesis.

Substrate specificity of the placental microsomal aromatase

Using an accurate and sensitive assay for the human placental aromatase we have found apparent Km values for androstenedione (4-androstene-3,17-dione) and testosterone to be 14 +/- 4.0 nM and 41 +/- 12 nM respectively. These values were significantly different (p < 0.001). Analyses at substrate concentrations 5-10 fold above and below the Km values did not indicate any anomalous kinetic behavior. Mixed substrate experiments were consistent with a single enzyme metabolizing both steroids: each competitively inhibited the aromatization of the other, and the "Ki" values were the same as their apparent Km values. Sodium chloride (1.2M) significantly increased the rate of testosterone aromatization by decreasing its Km value and had no significant effect on the aromatization of androstenedione. However, in the presence of this salt testosterone still inhibited the aromatization of androstenedione competitively with a "Ki" equal to its apparent Km. Our data is therefore consistent with the proposal that human placental microsomes contain a single "high affinity" site for the aromatization of androstenedione and testosterone.

In vitro conversion of pregnenolone to progesterone by term human fetal membranes

The conversion of pregnenolone to progesterone by homogenates of term human fetal membranes (38 to 40 weeks' gestation) was quantitated prior to and after labor. Chorion pars reflexa obtained after spontaneous labor by vaginal delivery was more active than that obtained prior to labor by elective cesarean section (p less than 0.05). With homogenates of amnion pars reflexa (n = 18), and pars placentaris (n = 18) obtained prior to labor no conversion or pregnenolone to progesterone was detected. In contrast, in amnion pars reflexa obtained after labor the reaction was detected in five of the 13 tissues examined and was significantly different from tissues obtained prior to labor (p less than 0.01). However, the conversion by the amnion pars placentaris after labor was not significantly different from that to labor. Evidence for inhibition of the reaction in the amnion pars reflexa and pars placentaris obtained prior to labor was found when prolonged washing of these tissues (up to 5 hours) with isotonic KCl resulted in the conversion of pregnenolone to progesterone being easily detected. This study suggests that there may be "activation" of the conversion of pregnenolone to progesterone in fetal membranes during labor and indicates that considerable care should be taken in studying this and perhaps other reactions in fetal membranes as the mode of delivery, the preparation of tissue, and, in the case of the amnion, the area studied can affect the results obtained.

3beta-Hydroxysteroid dehydrogenase activity in human fetal membranes

A 3beta-hydroxysteroid dehydrogenase (3betaHSD) was demonstrated in term human fetal membranes (chorion and amnion) with both dehydroepiandrosterone (3beta-hydroxy-5-androsten-17-one) and pregnenolone (3beta-hydroxy-5-pregnen-20-one as substrates, and the subcellular distribution substrate and nucleotide specificity of the enzyme was studied. In both membranes the microsomal fraction (particles which sedimented at 105,000 g after 90 min) had the highest specific activity. The chorion was more active than the amnion but the enzyme in both tissues had similar substrate and nucleotide specificity. NAD was the preferred cofactor, and pregnenolone was a better substrate than dehydroepiandrosterone in the presence of NAD. However, with NADP as cofactor both steroids were equally good substrates. When the 3beta-hydroxysteroid dehydrogenase activity of chorion microsomes was compared with that of placental microsomes, the specific activities were found to be of the same order of magnitude, and the substrate, nucleotide specificity and steroid binding properties were almost identical.