Purification and properties of cytochrome P-450 from homogenates of human fetal livers

Kitada, Munehiro; Kamataki, Tetsuya; Itahashi, Koshiro; Rikihisa, Tadaaki; Kato, Ryuichi; Kanakubo, Yoshio

doi:10.1016/0003-9861(85)90383-2

Cited by 131 publications

(48 citation statements)

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“…This suggested that CYP3A genes are transcribed in both adult and fetal livers but at different levels. However, an initial report of Kitada et al [51] indicated that the CYP3A7 protein represented less than 2-3% of the total P-450 in adult liver microsomes. Such a discrepancy between the amount of RNA encoding P-450 or epoxide hydrolase and the level of protein immunochemically detected in a same sample has already been reported and remains unexplained [19, 521. This raised questions about the suitability of available informations about the efficiency of biotransformation pathways.…”

Section: Discussionmentioning

confidence: 99%

Expression of CYP3A in the Human Liver — Evidence that the Shift between CYP3A7 and CYP3A4 Occurs Immediately After Birth

Lacroix

Sonnier

Moncion

et al. 1997

European Journal of Biochemistry

476

344

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CYP3A isoform? are responsible for the biotransformation of a wide variety of exogenous chemicals and endogenous steroids in human tissues. Two members of the CYP3A subfamily display developmentally regulated expression in the liver; CYP3A7 is expressed in the fetal liver, whereas CYP3A4 is the major cyrochrome P-450 isoform present in the adult liver. To gain insight into the descriptive ontogenesis of CYP3A isoforms during the neonatal period, we have developed several approaches to explore a neonatal liver bank. Although CYP3A4 and CYP3A7 are structurally closely related, they differ in their capacity to carry out monooxygenase reactions. We have cloned CYP3A4 and CYP3A7 and established stable transfectants in Ad293 cells to investigate their substrate specificities. The 16a hydroxylation of dehydroepiandrosterone is catalyzed by both proteins, but CYP3A7 has a higher affinity and maximal velocity than CYP3A4. Conversely, the conversion of testosterone into its 6p derivative is essentially supported by CYP3A4. We used these two probes to determine the ontogenic evolution at the protein level; CYP3A7 was very active in the fetal liver and its activity was maximal during the first week following birth before to progressively decline and reached a very low level in adult livers. Conversely, the activity of CYP3A4 was extremely weak in the fetus and began to raise after birth to reach 30-40% of the adult activity after one month.CYP3A4 RNA accumulation displays a similar pattern of evolution; when probed with an oligonucleotide, its concentration increased rapidly after birth to reach a plateau as soon as the first week of age.These data supports the assumption that CYP3A4 expression is transcriptionally activated during the first week after birth and is accompanied by a simultaneous decrease of CYP3A7 expression, in such a way that the overall CYP3A protein content and the level of pentoxyresorufin dealkylase catalyzed by the two proteins remain nearly constant.Keywords: ontogenesis ; human liver; CYP3A7, CYP3A4 ; dehydroepiandrosterone.The cytochrome P-450 (P-450) gene superfamily encodes a group of hemoproteins that mostly catalyze the oxidative metabolism of hydrophobic endogenous compounds such as steroids, fatty acids, prostaglandins and exogenous chemicals including drugs, carcinogens and environmental pollutants. These substrates can be converted in presence of NADPH and molecular oxygen either to inert polar metabolites, further eliminated in a water-soluble form, or to cytotoxic or carcinogenic derivatives. One feature of the P-450 system is its capacity to act on thousands of compounds and to carry out a multiplicity of reactions, generically termed monooxygenations. To cope with the large number of substrates and the wide diversity of their chemical structures, several isoforms of P-450 coexist [l, 21 and exhibit overlapping substrate specificities (for review, see [3]). In the human liver, one can consider that the major P-450 isoforms are members of the CYP2C and CYP3A subfamilies. They are constitu...

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Section: Discussionmentioning

confidence: 99%

Expression of CYP3A in the Human Liver — Evidence that the Shift between CYP3A7 and CYP3A4 Occurs Immediately After Birth

Lacroix

Sonnier

Moncion

et al. 1997

European Journal of Biochemistry

476

344

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“…Another crucial element is the maturity of the enzymatic system implicated in its metabolism. To date, only few data have reported the onset of P-450 isoenzymes in the human liver: these studies concluded on the presence of CYP3A protein in the fetal liver as early as the 14th week of gestation [2,[19][20][21][22][23] and the absence of proteins of the CYP2C subfamily, explaining the very low activity towards benzopyrene and mephenytoin [2, The CYP2D subfamily is a third group of P-450 genes, composed of three genes in the human species, but only one is functional 1241. We have accumulated evidence indicating that, during ontogenesis, the surge in CYP2D6 protein is mainly postnatal since its concentration rises in newborns 24 h after birth.…”

Section: Discussionmentioning

confidence: 99%

Expression of CYP2D6 in developing human liver

Tréluyer

Jacqz-Aigrain

Álvarez

et al. 1991

European Journal of Biochemistry

181

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The CYP2D6 protein is a polymorphic isoenzyme involved in the biotransformation of several drugs including the probe drug dextromethorphan. The rise in the protein concentration, immunochemically determined with a specific antibody, was shown to occur within the first week following birth, whatever the gestational age at birth.In fetuses, the concentration of hepatic CYP2D6 protein was very low or undetectable in 70% of samples tested. In the remaining 30%, its concentration was comparable to that of newborns aged 1 -7 days. This early rise was associated with spontaneous abortion in 70% of positive samples, whereas in fetuses with an intermediate CYP2D6 protein concentration, 80% were from induced abortions.The rise in CYP2D6 protein was associated with the developmental onset of dextromethorphan O-demethylation, but not N-demethylation, even if activity was lower in fetal than in neonatal and in adult liver microsomes.Lastly, the CYP2D6 RNA is detectable earlier than the protein and exhibits a peak of hepatic accumulation in newborns, before declining in adulthood. A positive correlation between RNA accumulation and protein concentration can be demonstrated only in the adult. This suggests that regulation is primarily at the transcriptional level, but cannot rule out the participation of post-transcriptional events in the regulation process throughout ontogenesis.Monooxygenase activities involved in the biotransformation of endogenous and exogenous hydrophobic molecules are mainly supported by cytochrome P-450 isoenzymes. To date, more than 30 isoenzymes of cytochrome P-450 have been identified, purified and/or cloned from the human liver (for review see [l]). These P-450s exhibit different profiles for their developmental evolution. In fetal liver, only one P-450 has been repeatedly detected: a CYP3A protein is present at a level roughly similar to that of the adult liver when determined by Western blotting [2] and is able to catalyze enzymatic activities like benzphetamine demethylation, aldrin epoxidation and dehydroepiandrosterone 16P-hydroxylation as the adult isoenzyme does. CYP2C8, one of the major P-450 isozymes immunologically detected in adult liver, is totally absent from fetal liver. The absence of this P-450 is responsible for the very low or negligible activity towards various substrates including mephenytoin, benzopyrene, p-nitroanisole [2, 31. To date, little or no data are available for other P-450 isoenzymes.We have focused our attention on CYP2D6, a gene coding for a polymorphic isoenzyme involved in the biotransformation of many drugs like P-blockers, tricyclic antidepressants, antitussives drugs, etc. In the adult Caucasian population, approximately 7% of individuals (poor vs extensive metabolizers) are defective in the active enzyme able to carry Enzymes. P-450, cytochrome P-450 (EC 1.14.14.1); isocitrate dehydrogenase (EC 1 .I .I .42). out the reaction [4]. This deficiency leads to an altered profile of urinary metabolites and consequently the ratio metabolite/ parent drug is markedly lo...

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“…CYP3A4 is the major cytochrome P450 in adult liver and constitutes 30-40% of the total liver CYP content (Shimada et al 1994). CYP3A7 is the major form in human embryonic, foetal and newborn liver (Kitada et al 1985;Kitada & Kamataki 1994;Lacroix et al 1997;de Wildt et al 1999b). In the period from late foetal to early neonatal life, there appears to be a peak in CYP3A7 activity, then a transition in expression and catalytic activity from predominant CYP3A7 to CYP3A4 such that the total hepatic CYP3A content appears to be relatively stable (Lacroix et al 1997;de Wildt et al 1999b).…”

Section: Cytochrome P450 In the Neonatal Human Livermentioning

confidence: 99%

Neonatal Hepatic Drug Elimination

Gow

Ghabrial

Smallwood

et al. 2001

Pharmacology & Toxicology

104

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After the transition from in utero to newborn life, the neonate becomes solely reliant upon its own drug clearance processes to metabolise xenobiotics. Whilst most studies of neonatal hepatic drug elimination have focussed upon in vitro expression and activities of drug-metabolising enzymes, the rapid physiological changes in the early neonatal period of life also need to be considered. There are dramatic changes in neonatal liver blood flow and hepatic oxygenation due to the loss of the umbilical blood supply, the increasing portal vein blood flow, and the gradual closure of the ductus venosus shunt during the first week of life. These changes which may well affect the capacity of neonatal hepatic drug metabolism. The hepatic expression of cytochromes P450 1A2, 2C, 2D6, 2E1 and 3A4 develop at different rates in the postnatal period, whilst 3A7 expression diminishes. Hepatic glucuronidation in the human neonate is relatively immature at birth, which contrasts with the considerably more mature neonatal hepatic sulfation activity. Limited in vivo studies show that the human neonate can significantly metabolise xenobiotics but clearance is considerably less compared with the older infant and adult. The neonatal population included in pharmacological studies is highly heterogeneous with respect to age, body weight, ductus venosus closure and disease processes, making it difficult to interpret data arising from human neonatal studies. Studies in the perfused foetal and neonatal sheep liver have demonstrated how the oxidative and conjugative hepatic elimination of drugs by the intact organ is significantly increased during the first week of life, highlighting that future studies will need to consider the profound physiological changes that may influence neonatal hepatic drug elimination shortly after birth.The development of clinical pharmacology has resulted in a more rational approach to drug therapy, as well as a deeper understanding of the factors capable of influencing drug disposition, and hence drug effects. Of these factors, age is of great importance. However, substantial differences in drug disposition not only exist between neonates and adults, but also among premature neonates, term neonates, infants and children.During the last two decades drug disposition in the neonatal period has been studied extensively. A major impetus for these studies seems to have been a series of incidents involving illness or death following the administration of drugs at ratios of dose/body weight innocuous in an adult (Craft et al. 1974;Gershanik et al. 1982). These studies have shown that the transition from neonate to childhood is characterised by the ontogeny of all of the processes of drug absorption, distribution, hepatic metabolism and renal excretion, with the development of hepatic drug metabolism being particularly important.The extent to which the neonatal drug-metabolising en-

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Purification and properties of cytochrome P-450 from homogenates of human fetal livers

Cited by 131 publications

References 29 publications

Expression of CYP3A in the Human Liver — Evidence that the Shift between CYP3A7 and CYP3A4 Occurs Immediately After Birth

Expression of CYP3A in the Human Liver — Evidence that the Shift between CYP3A7 and CYP3A4 Occurs Immediately After Birth

Expression of CYP2D6 in developing human liver

Neonatal Hepatic Drug Elimination

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