Transplacental transfer and metabolism of 17-alpha-hydroxyprogesterone caproate

Performance on a modified signal detection task of attention is impaired in male and female rats following developmental exposure to the synthetic progestin, 17α-hydroxyprogesterone caproate

Based on evidence that the developing mesocortical dopamine pathway is sensitive to progestins, in the present study we tested the hypothesis that attention, a fundamental component of successful cognitive behavior, is disrupted by developmental exposure to the synthetic progestin, 17-α-hydroxyprogesterone caproate (17-OHPC). To assess attentional impairments, a modified signal detection task was utilized with three stimulus modalities: compound (light and tone), light alone, and tone alone, for four stimulus durations (2, 0.5, 0.25, 0.125 s). Adult rats were trained to push one lever if they detected the stimulus, and another lever if the stimulus was not presented. 17-OHPC animals were able to attend to the task, as evidenced by similar correct responses as controls. However, as the task became increasingly difficult at shorter durations, 17-OHPC animals made significantly more omissions compared to controls, suggesting that 17-OHPC treatment may disrupt attentional processes and/or delay response time. These findings add to the current body of literature demonstrating that exposure to 17-OHPC during development produces deficits in cognitive behavior in adulthood. These results may inform potential risks associated with 17-OHPC treatment in pregnant women with a history of preterm delivery who are commonly recipients of such treatment.

Developmental exposure to the synthetic progestin, 17α-hydroxyprogesterone caproate, disrupts the mesocortical serotonin pathway and alters impulsive decision-making in rats

The synthetic progestin, 17α-hydroxyprogesterone caproate (17-OHPC), is administered to women at risk for preterm birth during a critical period of fetal development for mesocortical pathways. Yet, little information is available regarding the potential effects of 17-OHPC on the developing fetal brain. In rat models, the mesocortical serotonin pathway is sensitive to progestins. Progesterone receptor (PR) is expressed in layer 3 pyramidal neurons of medial prefrontal cortex (mPFC) and in serotonergic neurons of the dorsal raphe. The present study tested the hypothesis that exposure to 17-OHPC during development disrupts serotonergic innervation of the mPFC in adolescence and impairs behavior mediated by this pathway in adulthood. Administration of 17-OHPC from postnatal days 1-14 decreased the density of SERT-ir fibers within superficial and deep layers and decreased the density of synaptophysin-ir boutons in all layers of prelimbic mPFC at postnatal day 28. In addition, rats exposed to 17-OHPC during development were less likely to make impulsive choices in the Delay Discounting task, choosing the larger, delayed reward more often than controls at moderate delay times. Interestingly, 17-OHPC exposed rats were more likely to fail to make any choice (i.e., increased omissions) compared to controls at longer delays, suggesting disruptions in decision-making. These results suggest that further investigation is warranted in the clinical use of 17-OHPC to better inform a risk/benefit analysis of progestin use in pregnancy.

Drug development research in pregnant and lactating women

Pregnant and lactating women are considered "therapeutic orphans" because they generally have been excluded from clinical drug research and the drug development process owing to legal, ethical, and safety concerns. Most medications prescribed for pregnant and lactating women are used "off-label" because most of the clinical approved medications do not have appropriate drug labeling information for pregnant and lactating women. Medications that lack human safety data on use during pregnancy and lactation may pose potential risks for adverse effects in pregnant and lactating women as well as risks of teratogenic effects to their unborn and newborn babies. Federal policy requiring the inclusion of women in clinical research and trials led to considerable changes in research design and practice. Despite more women being included in clinical research and trials, the inclusion of pregnant and lactating women in drug research and clinical trials remains limited. A recent revision to the "Common Rule" that removed pregnant women from the classification as a "vulnerable" population may change the culture of drug research and drug development in pregnant and lactating women. This review article provides an overview of medications studied by the Obstetric-Fetal Pharmacology Research Units Network and Centers and describes the challenges in current obstetrical pharmacology research and alternative strategies for future research in precision therapeutics in pregnant and lactating women. Implementation of the recommendations of the Task Force on Research Specific to Pregnant Women and Lactating Women can provide legislative requirements and opportunities for research focused on pregnant and lactating women.

Sex differences in dopamine innervation and microglia are altered by synthetic progestin in neonatal medial prefrontal cortex

The synthetic progestin 17-α-hydroxyprogesterone caproate (17-OHPC) is commonly prescribed to pregnant women with a history of preterm delivery, despite little evidence of efficacy. The timing of 17-OHPC administration coincides with fetal mesocortical dopamine pathway development, yet the potential effects on cortical development and cognition are almost unknown. In rodent models, exposure to 17-OHPC significantly increased dopaminergic innervation of the medial prefrontal cortex (mPFC), an aberrant pattern of connectivity that may underlie deficits in cognitive flexibility observed in adulthood. In the present study, tyrosine hydroxylase (TH) immunoreactivity was used to determine whether 17-OHPC altered dopaminergic innervation of the mPFC during a neonatal period of synaptogenesis in males and females. Although there were no differences in the amount of TH-immunoreactive (-IR) fibres, there was a sex difference in TH-IR fibre distribution in deep layers of the prelimbic area (PL) mPFC; males had a narrower pattern of dopaminergic innervation than females. 17-OHPC exposure abolished these sex-specific patterns, such that 17-OHPC females had a narrower pattern in the PL than control females. In the infralimbic mPFC (IL), 17-OHPC males had a broader pattern of distribution of TH-immunoreactivity than control males with no differences in the amount of TH-IR fibres. 17-OHPC also created a sex difference in which males had a lower TH-IR fibre density than females. We also examined microglia, brain macrophages that play a key role in sculpting dopaminergic axon outgrowth in development, using phenotype as an indirect measure of microglial activity. Females had a greater number of reactive stout microglia compared to males in the PL, and males had more active round microglia than females in the IL. 17-OHPC treatment abolished the sex differences in both regions. These findings demonstrate that developmental exposure to 17-OHPC can exert differential effects in males and females and may diminish sex differences in cortical maturation.

Developmental exposure to 17α-hydroxyprogesterone caproate impairs adult delayed reinforcement and reversal learning in male and female rats

Women with a history of unexplained miscarriage are frequently prescribed the synthetic progestin, 17α-hydroxyprogesterone caproate (17-OHPC) during the middle trimester of pregnancy. However, little is known about the long-term behavioural effects of 17-OHPC. Work in rodents suggests that the developing brain is sensitive to progestins. Neonatal 17-OHPC impairs adult performance in set-shifting and delay discounting. The present study tested the effects of 17-OHPC (0.5 mg kg^-1 ) or vehicle administration from postnatal days 1-14 on cognitive function in adulthood in rats. Cognitive function was assessed in males and females (n = 8-10 per group) by operant responding for sugar pellets, measuring delayed reinforcement or reversal learning. For delayed reinforcement, the rat must wait 15 seconds for pellets after responding on a lever. Delay is signalled by a light or is unsignalled. For reversal learning, the rat must respond on the lever under a stimulus light, and then learn to respond on the unlit lever. For delayed reinforcement, rats earned more pellets under signalled vs unsignalled conditions. Likewise, males made more responses and earned more pellets compared to females. Under signalled conditions, 17-OHPC-treated rats earned fewer pellets than controls. For reversal learning, the results were similar. Females required more trials than males to respond correctly for the new rule, and 17-OHPC-treated rats required more trials than controls. This suggests that 17-OHPC exposure during development may impair cognitive function. Considering that questions have been raised as to the efficacy of 17-OHPC to prevent miscarriage, it may be necessary to rethink the use of progestin therapy during pregnancy.

Effect of progesterone on Smad signaling and TGF-β/Smad-regulated genes in lung epithelial cells

The effect of endogenous progesterone and/or exogenous pre- or postnatal progesterone application on lung function of preterm infants is poorly defined. While prenatal progesterone substitution may prevent preterm birth, in vitro and in vivo data suggest a benefit of postnatal progesterone replacement on the incidence and severity of bronchopulmonary dysplasia (BPD). However, the molecular mechanisms responsible for progesterone's effects are undefined. Numerous factors are involved in lung development, airway inflammation, and airway remodeling: the transforming growth factor beta (TGF-β)/mothers against decapentaplegic homolog (Smad) signaling pathway and TGF-β-regulated genes, such as connective tissue growth factor (CTGF), transgelin (TAGLN), and plasminogen activator inhibitor-1 (PAI-1). These processes contribute to the development of BPD. The aim of the present study was to clarify whether progesterone could affect TGF-β1-activated Smad signaling and CTGF/transgelin/PAI-1 expression in lung epithelial cells. The pharmacological effect of progesterone on Smad signaling was investigated using a TGF-β1-inducible luciferase reporter and western blotting analysis of phosphorylated Smad2/3 in A549 lung epithelial cells. The regulation of CTGF, transgelin, and PAI-1 expression by progesterone was studied using a promoter-based luciferase reporter, quantitative real-time PCR, and western blotting in the same cell line. While progesterone alone had no direct effect on Smad signaling in lung epithelial cells, it dose-dependently inhibited TGF-β1-induced Smad3 phosphorylation, as shown by luciferase assays and western blotting analysis. Progesterone also antagonized the TGF-β1/Smad-induced upregulation of CTGF, transgelin, and PAI-1 at the promoter, mRNA, and/or protein levels. The present study highlights possible new molecular mechanisms involving progesterone, including inhibition of TGF-β1-activated Smad signaling and TGF-β1-regulated genes involved in BPD pathogenesis, which are likely to attenuate the development of BPD by inhibiting TGF-β1-mediated airway remodeling. Understanding these mechanisms might help to explain the effects of pre- or postnatal application of progesterone on lung diseases of preterm infants.

Placental control of drug delivery

The placenta serves as the interface between the maternal and fetal circulations and regulates the transfer of oxygen, nutrients, and waste products. When exogenous substances are present in the maternal bloodstream-whether from environmental contact, occupational exposure, medication, or drug abuse-the extent to which this exposure affects the fetus is determined by transport and biotransformation processes in the placental barrier. Advances in drug delivery strategies are expected to improve the treatment of maternal and fetal diseases encountered during pregnancy.

Administration of Progesterone Throughout Pregnancy Increases Maternal Steroids Without Adverse Effect on Mature Oligodendrocyte Immunostaining in the Guinea Pig

Progesterone is administered to pregnant women at risk of premature labor, despite systematic reviews showing conflicting outcomes regarding its use, highlighting doubt over the effectiveness of the therapy. Progesterone can be rapidly metabolized into a number of steroids, but to date, there has been a lack of investigation into the fetal steroid profiles following administration and whether this impacts fetal neurodevelopment. The objective of this study was to determine the effect of progesterone treatment on allopregnanolone and cortisol levels in the fetus and on a marker of myelination in the fetal brain. We used a guinea pig model where pregnant dams were administered vehicle (β-cyclodextrin) or progesterone orally throughout pregnancy (GA29-61). Maternal and fetal fluids and tissues were collected at both preterm (GA61) and term (GA68) ages. Maternal and fetal progesterone and cortisol were analyzed by enzyme immunoassay and allopregnanolone by radioimmunoassay. Measurement of myelination of fetal brains (hippocampus, cingulum, and subcortical white matter) at preterm and term ages was performed by immunohistochemistry staining for myelin basic protein. We found that dams receiving progesterone had significantly elevated progesterone and cortisol concentrations, but there was no effect on allopregnanolone. Interestingly, the increased cortisol concentrations were not reflected in the fetuses, and there was no effect of progesterone treatment on myelination. Therefore, we conclude that in our guinea pig model, maternal administration of progesterone has no effect on cortisol levels or markers of mature oligodendrocytes in the fetus and suggest this is potentially due to the protective cortisol barrier in the placenta.

Progesterone from maternal circulation binds to progestin receptors in fetal brain

Steroid hormones activate nuclear receptors which, as transcription factors, can regulate critical aspects of neural development. Many regions of the rat forebrain, midbrain and hindbrain express progestin receptors (PR) during perinatal life, suggesting that progesterone may play an important role in the development of the brain. An immunohistochemical approach using two antibodies with differential recognition of ligand-bound PR was used to examine whether fetuses are exposed to maternal progesterone during pregnancy and whether progesterone from maternal circulation can bind to PR within the fetal brain. Findings demonstrate that maternal and fetal serum progesterone levels are positively correlated at the end of gestation, suggesting a common source of progesterone in mothers and fetuses (e.g., the maternal ovary). Additional findings suggest that administration of exogenous progesterone to mothers not only increases fetal serum progesterone levels within 2 h, but appears to increase ligand-bound PR in fetal brain. These findings suggest that progesterone of maternal origin may play a previously overlooked role in neural development. In addition, there are implications for the ongoing prophylactic use of synthetic progestins in pregnant women for the prevention of premature birth. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 77: 767-774, 2017.

Population pharmacokinetics of 17α-hydroxyprogesterone caproate in singleton gestation

AIMS

17α-hydroxyprogesterone caproate (17-OHPC) reduces the rate of preterm birth in women with a prior preterm birth. Limited data exist on the pharmacokinetics (PK) of 17-OHPC or the plasma concentrations achieved during therapy. In this study, we evaluated the population PK of 17-OHPC in pregnant subjects with singleton gestation and also evaluated intrinsic and extrinsic factors that may potentially affect 17-OHPC PK in this patient population.

METHODS

Sixty-one women with singleton pregnancies participated in this trial. Subjects received weekly intramuscular injections of 250 mg 17-OHPC in 1 ml castor oil from the time of enrolment (16 0/7 weeks - 20 6/7 weeks) up to 35 weeks gestation or until delivery. Blood samples were obtained between 24 and 28 weeks, between 32 and 35 weeks and over a 28-day period beyond the last injection. Maternal and/or cord blood were obtained at delivery. Data analysis was performed by nonlinear mixed effects modelling (NONMEM(®) ).

RESULTS

The 17-OHPC PK were best described by a model with one maternal compartment and one fetal compartment, with first-order absorption and elimination from the maternal compartment. Maternal body weight was a significant covariate for both clearance (CL/F) and volume of distribution (Vmaternal /F). The final population mean estimates were: CL/F 1797 l/d, Vmaternal /F 32 610 l and mother to cord rate constant 0.005 day(-1) . This report describes for the first time the population PK of 17-OHPC in singleton pregnancy.

CONCLUSIONS

The population PK study reported here represents the initial steps in understanding and optimizing 17-OHPC therapy for preventing preterm birth.

Exposure to the Synthetic Progestin, 17α-Hydroxyprogesterone Caproate During Development Impairs Cognitive Flexibility in Adulthood

The synthetic progestin, 17α-hydroxyprogesterone caproate, is increasingly used for the prevention of premature birth in at-risk women, despite little understanding of the potential effects on the developing brain. Rodent models suggest that many regions of the developing brain are sensitive to progestins, including the mesocortical dopamine pathway, a neural circuit important for complex cognitive behaviors later in life. Nuclear progesterone receptor is expressed during perinatal development in dopaminergic cells of the ventral tegmental area that project to the medial prefrontal cortex. Progesterone receptor is also expressed in the subplate and in pyramidal cell layers II/III of medial prefrontal cortex during periods of dopaminergic synaptogenesis. In the present study, exposure to 17α-hydroxyprogesterone caproate during development of the mesocortical dopamine pathway in rats altered dopaminergic innervation of the prelimbic prefrontal cortex and impaired cognitive flexibility with increased perseveration later in life, perhaps to a greater extent in males. These studies provide evidence for developmental neurobehavioral effects of a drug in widespread clinical use and highlight the need for a reevaluation of the benefits and potential outcomes of prophylactic progestin administration for the prevention of premature delivery.

Basic obstetric pharmacology

Pregnancy is associated with a variety of physiological changes that can alter the pharmacokinetics and pharmacodynamics of several drugs. However, limited data exists on the pharmacokinetics and pharmacodynamics of the majority of the medications used in pregnancy. In this article, we first describe basic concepts (drug absorption, bioavailability, distribution, metabolism, elimination, and transport) in pharmacokinetics. Then, we discuss several physiological changes that occur during pregnancy that theoretically affect absorption, distribution, metabolism, and elimination. Further, we provide a brief review of the literature on the clinical pharmacokinetic studies performed in pregnant women in recent years. In general, pregnancy increases the clearance of several drugs and correspondingly decreases drug exposure during pregnancy. Based on current drug exposure measurements during pregnancy, alterations in the dose or dosing regimen of certain drugs are essential during pregnancy. More pharmacological studies in pregnant women are needed to optimize drug therapy in pregnancy.

Critical appraisal of the efficacy, safety, and patient acceptability of hydroxyprogesterone caproate injection to reduce the risk of preterm birth

Prevention of preterm delivery is a major desiderate in contemporary obstetrics and a societal necessity. The means to achieve this goal remain elusive. Progesterone has been used in an attempt to prevent preterm delivery since the 1970s, but the evidence initially accumulated was fraught by mixed results and was based on mostly underpowered studies with variable eligibility criteria, including history of spontaneous abortion as an indication for treatment. More recent randomized controlled clinical trials restimulated the interest in progesterone supplementation, suggesting that progesterone may favorably influence the rate of preterm delivery. Preterm delivery is a complex disorder and consequently it is unlikely that one generalized prevention strategy will be effective in all patients. Further, an additional impediment in accepting progesterone as the "magic bullet" in the prevention of preterm delivery is that its mechanism of action is not fully understood and the optimal formulations, route of administration, and dose have yet to be established. We have concerned ourselves in this review with the most recent status of 17 alpha-hydroxyprogesterone caproate (17OH-PC) supplementation for prevention of preterm delivery. Our intention is to emphasize the efficacy, safety, and patient acceptability of this intervention, based on a comprehensive and unbiased review of the available literature. Currently there are insufficient data to suggest that 17OH-PC is superior or inferior to natural progesterone. Based on available evidence, we suggest a differential approach giving preferential consideration to either 17OH-PC or other progestins based on obstetric history and cervical surveillance. Progestin therapy for risk factors other than a history of preterm birth and/or a short cervix in the current pregnancy is not currently supported by the published evidence. The experience to date with 17OH-PC indicates that there are population subgroups that may be harmed by administration of 17OH-PC. Therefore, extending the use of 17OH-PC to unstudied populations or for indications that are not evidence-based is inadvisable outside of a research protocol.

Pharmacology and placental transport of 17-hydroxyprogesterone caproate in singleton gestation

OBJECTIVE

The purpose of this study was to estimate pharmacokinetic parameters and to evaluate placental transport of 17-hydroxyprogesterone caproate (17-OHPC) in singleton gestation.

STUDY DESIGN

Sixty-one women who received weekly injections of 17-OHPC underwent 2 pharmacokinetic studies at 20 + 0 to 24 + 6 weeks' gestation (study 1) and 31 + 0 to 34 + 6 weeks' gestation (study 2); daily blood samples were obtained between injections. In 18 women, blood samples were obtained over a 28-day period beyond the last injection (extended study). Maternal and/or cord blood were obtained at delivery.

RESULTS

The half-life (median ± SD) of 17-OHPC was 16.2 ± 6 days. Concentrations of 17-OHPC were higher during study 2 than during study 1. Body mass index affected maternal 17-OHPC concentrations. Cord:maternal 17-OHPC concentration ratios averaged 0.2; 17-OHPC was detectible in cord plasma 44 days after the last maternal injection.

CONCLUSION

The apparent half-life of 17-OHPC is long, and pharmacokinetic parameters vary widely between subjects and are affected by maternal body mass index. The drug crosses the placental barrier.

17-α hydroxyprogesterone caproate for the prevention of preterm birth

17 α hydroxyprogesterone caproate is a synthetic form of the natural progestin 17-α hydroxyprogesterone that is US FDA approved for the prevention of recurrent spontaneous preterm birth in women with a history of a prior singleton preterm birth. For women with a history of a prior spontaneous preterm birth between 20 weeks and 36 weeks and 6 days of gestation, the use of 17-α hydroxyprogesterone caproate has been shown to reduce the risk of recurrent preterm birth by more than 30%. This medication is the only drug currently FDA approved for the prevention of preterm birth, and it is the first drug the FDA has approved for use exclusively during pregnancy in approximately 15 years.

Metabolism of 17-alpha-hydroxyprogesterone caproate by human placental mitochondria

Perfusion of 17-alpha-hydroxyprogesterone caproate (17HPC) via the maternal circuit of a dually perfused human placental lobule resulted in the extensive formation of 2 metabolites. On the other hand, human placental microsomes biotransformed 17HPC into 5 monohydroxylated metabolites, which did not correspond to those formed during perfusion. The goal of this investigation was to determine the subcellular localization of the enzymes responsible for the biotransformation of 17HPC during its perfusion in human placenta. Crude subcellular fractions of the human placental tissue were utilized. Six 17HPC metabolites were formed by the placental mitochondrial fraction, of which 4 were identical to those formed by the microsomes; whereas the other 2, namely MM and M₁₉, were formed by the mitochondrial fraction only. The latter metabolites were identical to those formed during 17HPC perfusion, as determined by liquid chromatography-mass spectrometry (LC-MS) analysis. Therefore, these data strongly suggest that the enzymes responsible for the biotransformation of 17HPC during its perfusion are predominantly localized in human placental mitochondria.

17 α-Hydroxyprogesterone caproate (Makena™): in the prevention of preterm birth

17 α-hydroxyprogesterone caproate is a synthetic progestin of which there is now a US FDA-approved formulation available for intramuscular administration (Makena™) to reduce the risk of preterm birth. Intramuscular 17 α-hydroxyprogesterone caproate (identical in formulation and manufacturing process to Makena™, thus hereafter referred to as Makena™) 250 mg once weekly, initiated at 16-20 weeks' gestation, was effective in reducing the risk of preterm birth in women with a singleton pregnancy at high risk of delivering preterm in a large, well designed, placebo-controlled trial (n = 463 randomized). Rates of delivery before 37 (primary endpoint), 35, or 32 weeks' gestation were significantly lower with Makena™ than with placebo, corresponding to relative risk reductions of 34%, 33%, and 42%, respectively. The benefit of the drug in reducing the risk of preterm birth was observed when deliveries were spontaneous (but not when indicated because of complications) and regardless of maternal race. In addition, there was a significantly lower rate of several adverse fetal/neonatal outcomes among infants of women who received Makena™ than among infants of placebo recipients, including necrotizing enterocolitis, need for supplemental oxygen, birth weight of <2500 g, and intraventricular hemorrhage. Makena™ was generally well tolerated in pregnant women in this trial. Moreover, fetal exposure to the drug appeared to be safe according to a 2- to 5-year follow-up of the study, with no evidence of a detrimental effect of the drug on child neurodevelopment and a low overall incidence (≈2%) of reproductive or genital abnormalities that was not significantly different from placebo.

Progesterone supplementation and the prevention of preterm birth

Preterm birth is currently the most important problem in maternal-child health in the United States and possibly throughout the world. It complicates one in eight US deliveries, and accounts for over 85% of all perinatal morbidity and mortality. Although survival of preterm infants has increased steadily over the past four decades-due in large part to the use of antenatal corticosteroids, improvements in neonatal resuscitation, and the introduction of neonatal intensive care units-efforts to prevent preterm birth have been largely unsuccessful. On February 3, 2011, the US Food and Drug Administration (FDA) approved the use of progesterone supplementation (hydroxyprogesterone caproate) during pregnancy to reduce the risk of recurrent preterm birth in women with a history of at least one prior spontaneous preterm delivery. This is the first time that the FDA has approved a medication for the prevention of preterm birth, and represents the first approval of a drug specifically for use in pregnancy in almost 15 years. This article reviews the evidence behind the use of progesterone for the prevention of preterm birth, and provides guidelines for the use of progesterone supplementation in clinical practice. A number of areas of ongoing controversy are addressed, including the optimal formulation and route of administration, the safety of progesterone supplementation in pregnancy, and its proposed mode of action.

Antibiotic Treatment of Dogs and Cats during Pregnancy

The use of pharmacological agents in pregnant females poses a major clinical challenge due to the marked physiological changes that may modify the pharmacokinetics of drugs and to the potential effects on the fetus. The purpose of this paper is to review briefly our knowledge on the use of antibacterial drugs during pregnancy and to provide information for the judicious selection of an antimicrobial treatment for use in pregnant bitches and queens. The risk to the fetus is a result of the ability of a drug to reach the fetal circulation and to produce toxic effects. The placenta functions as a barrier that protects the fetus due to the presence of transporters and metabolising enzymes; however, during pregnancy, the presence and activity of both enzymes and transporters may change. Antimicrobial agents that have been shown to be safe for use during pregnancy include betalactams, macrolides, and lincosamides. Pharmacotherapy during pregnancy in all species may affect adversely the developing fetus; therefore, it should be avoided when possible.

Bupropion metabolism by human placenta

Smoking during pregnancy is the largest modifiable risk factor for pregnancy-related morbidity and mortality. The success of bupropion for smoking cessation warrants its investigation for the treatment of pregnant patients. Nevertheless, the use of bupropion for the treatment of pregnant smokers requires additional data on its bio-disposition during pregnancy. Therefore, the aim of this investigation was to determine the metabolism of bupropion in placentas obtained from nonsmoking and smoking women, identify metabolites formed and the enzymes catalyzing their formation, as well as the kinetics of the reaction. Data obtained revealed that human placentas metabolized bupropion to hydroxybupropion, erythro- and threohydrobupropion. The rates for formation of erythro- and threohydrobupropion exceeded that for hydroxybupropion by several folds, were dependent on the concentration of bupropion and exhibited saturation kinetics with an apparent K(m) value of 40microM. Human placental 11beta-hydroxysteroid dehydrogenases were identified as the major carbonyl-reducing enzymes responsible for the reduction of bupropion to threo- and erythrohydrobupropion in microsomal fractions. On the other hand, CYP2B6 was responsible for the formation of OH-bupropion. These data suggest that both placental microsomal carbonyl-reducing and oxidizing enzymes are involved in the metabolism of bupropion.

Continuous infusion of 17-hydroxyprogesterone caproate into either the fetoplacental or intervillous circulation of a placental cotyledon attenuates vasoconstriction of the fetoplacental arteries by thromboxane mimetic U46619

OBJECTIVE

The objective of the study was to determine whether pretreatment of fetal or maternal placental vasculature with 17-hydroxyprogesterone caproate (17-P) attenuates the vasoactive effect of the thromboxane mimetic U46619.

STUDY DESIGN

Two cotyledons were obtained from each placenta studied. For the first 5 placentas, the fetal artery of 1 cotyledon from each pair was infused with 17-P. After 30 minutes, a bolus dose of U46619 was administered to both cotyledons. An identical procedure was carried out on the next 5 placentas except that 17-P was infused into the intervillous space.

RESULTS

The pressure excursion caused by bolus administration of U46619 was less in the cotyledons infused with 17-P, both in the 5 cases in which the fetal vasculature was infused with 17-P (P = .0035) and in the 5 cases in which the maternal vasculature was infused with 17-P (P = .038).

CONCLUSION

Pretreatment of either the fetal or maternal circuits of the placenta with 17-P attenuates U46619-mediated fetoplacental vasoconstriction.

Modeling placental transport: correlation of in vitro BeWo cell permeability and ex vivo human placental perfusion

The placental passage of three compounds with different physicochemical properties was recently investigated in ex vivo human placental perfusion experiments (caffeine, benzoic acid, and glyphosate) [Mose, T., Kjaerstad, M.B., Mathiesen, L., Nielsen, J.B., Edelfors, S., Knudsen, L.E., 2008. Placental passage of benzoic acid, caffeine, and glyphosate in an ex vivo human perfusion system. J. Toxicol. Environ. Health, Part A 71, 984-991]. In this work, the transport of these same three compounds, plus the reference compound antipyrine, was investigated using BeWo (b30) cell monolayers. Transport across the BeWo cells was observed in the rank order of caffeine>antipyrine>benzoic acid>glyphosate in terms of both the apparent permeability coefficient and the initial slope, defined as the linear rate of substance transferred to the fetal compartment as percent per time, a parameter used to compare the two experimental models. The results from the in vitro studies were in excellent agreement with the ex vivo results (caffeine approximately antipyrine>benzoic acid>glyphosate). However the transfer rate was much slower in the BeWo cells compared to the perfusion system. The advantages and limitations of each model are discussed in order to assist in the preparation, prediction, and performance of future studies of maternal-fetal transfer.

Metabolism of 17alpha-hydroxyprogesterone caproate by hepatic and placental microsomes of human and baboons

Recent data from our laboratory revealed the formation of an unknown metabolite of 17 hydroxyprogesterone caproate (17-HPC), used for treatment of preterm deliveries, during its perfusion across the dually perfused human placental lobule. Previously, we demonstrated that the drug is not hydrolyzed, neither in vivo nor in vitro, to progesterone and caproate. Therefore, the hypothesis for this investigation is that 17-HPC is actively metabolized by human and baboon (Papio cynocephalus) hepatic and placental microsomes. Baboon hepatic and placental microsomes were investigated to validate the nonhuman primate as an animal model for drug use during pregnancy. Data presented here indicate that human and baboon hepatic microsomes formed several mono-, di-, and tri-hydroxylated derivatives of 17-HPC. However, microsomes of human and baboon placentas metabolized 17-HPC to its mono-hydroxylated derivatives only in quantities that were a fraction of those formed by their respective livers, except for two metabolites (M16' and M17') that are unique for placenta and contributed to 25% and 75% of the total metabolites formed by human and baboon, respectively. The amounts of metabolites formed, relative to each other, by human and baboon microsomes were different suggesting that the affinity of 17-HPC to CYP enzymes and their activity could be species-dependent.