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Biomedical subjects

D Kupfer

Publications and source records attributed to D Kupfer.

At least 73 records · Page 4Linked to original sources
PubMed1982

Hydroxylation of prostaglandins by inducible isozymes of rabbit liver microsomal cytochrome P-450. Participation of cytochrome b5.

The hydroxylation of prostaglandin (PG) E1, PGE2, and PGA1 was investigated in a reconstituted rabbit liver microsomal enzyme system containing phenobarbital-inducible isozyme 2 or 5,6-benzoflavone-inducible isoenzyme 4 of P-450, NADPH-cytochrome P-450 reductase, phosphatidylcholine, and NADPH. Significant metabolism of prostaglandins by isozyme 2 occurred only in the presence of cytochrome b5. Under these conditions, PGE1 hydroxylation was linear with time (up to 45 min) and protein concentration, and maximal rates were obtained with a 1:1:2 molar ratio of reductase: cytochrome b5:P-450LM2. Moreover, P-450LM2 catalyzed the conversion of PGE1, PGE2, and PGA1 to the respective 19- and 20-hydroxy metabolites in a ratio of about 5:1, and displayed comparable activities toward the three prostaglandins based on the total products formed in 60 min. Apocytochrome b5 or ferriheme could not substitute for intact cytochrome b5, while reconstitution of apocytochrome b5 with ferriheme led to activities similar to those obtained with the native cytochrome. Isozyme 4 of P-450 differed markedly from isozyme 2 in that it catalyzed prostaglandin hydroxylation at substantial rates in the absence of cytochrome b5, was regiospecific for position 19 of all three prostaglandins, and had an order of activity of PGA1 greater than PGE1 greater than PGE2. P-450LM4 preparations from untreated and induced animals had similar activities with PGE1 and PGE2, respectively. Addition of cytochrome b5 resulted in a 20 to 30% increase in the rate of PGE1 hydroxylation and an appreciably greater enhancement in the extent of all the P-450LM4-catalyzed reactions, the stimulation being greatest with PGE2 (3-fold) and least with PGA1 (1.6-fold). Cytochrome b5 was thus required for maximal metabolism of all three prostaglandins, but did not alter the regiospecificity or the order of activity of P-450 isozyme 4 with the individual substrates. In the presence of cytochrome b5, the prostaglandin hydroxylase activities of isozyme 4 were two to six times higher than those of isozyme 2.

Alprostadil↗
PubMed1982

Interaction of EEG sleep, antidepressants, and affective disease.

The major sleep characteristics of depression are summarized and new EEG sleep studies of antidepressants, including preliminary data on desipramine and zimelidine, are described. The relationship of steady-state plasma amitriptyline levels to REM sleep and the use of EEG sleep measures as predictors of clinical response to tricyclics will also be discussed. The effects of antidepressant agents on sleep are immediate and pronounced, and studies of these drug-induced effects may also represent a rational method for drug classification.

Amitriptyline↗
PubMed1982

beta-Diethylaminoethyl-2, 2-diphenylpentanoate (SKF 525-A)-mediated translocation of uterine estrogen receptor from the cytosolic to the nuclear compartment in isolated rat uteri.

The current study examines whether beta-diethylaminoethyl-2, 2-diphenylpentanoate (SKF 525-A), a recognized inhibitor of microsomal monooxygenase activity, interacts with the uterine estrogen receptor in a manner similar to that of classical estrogens. Incubation of SKF 525-A with isolated uteri from immature rats diminished the levels of cytosolic estrogen receptor and increased the amount of nuclear estrogen receptor. Similar results were obtained with uteri from ovariectomized or ovariectomized and adrenalectomized rats, indicating that the action of SKF 525-A did not depend on the availability of ovarian or adrenal hormones. Additionally, experiments with uterine cytosol from immature rats, employing analysis by Scatchard and Lineweaver-Burk plots, demonstrated that SKF 525-A (0.05 mM) competitively inhibited [3H] estradiol binding to the estrogen receptor, suggesting that both compounds bind to the same site on the receptor. The Ki for SKF 525-A was determined to be 100 micrometers, indicating that SKF 525-A has a relatively low affinity for the receptor. Further confirmation of this finding was obtained by assessing the relative inhibition of [3H] estradiol binding to uterine cytosol estrogen receptor by SKF 525-A versus that of unlabeled estradiol. The affinity of SKF 525-A for the estrogen receptor appears to be about 0.001% that of estradiol. These studies demonstrate that, like estradiol, SKF 525-A interacts with the estrogen receptor. Additionally, it was concluded that the "estrogenic" (uterotropic) activity observed in vivo [Calhoun et al. Proc. Soc. Exp. Biol. Med. 136:47 to 50 (1971)] with SKF 525-A, is mediated through the uterine estrogen receptor.

Adrenalectomy↗
PubMed1979

Effect of inducers and inhibitors of monooxygenase on the hydroxylation of prostaglandins in the guinea pig. Evidence for several monooxygenases catalyzing omega- and omega-1-hydroxylation.

The incubation of prostaglandins (PG's) with liver microsomes from guinea pigs treated with inducers of monooxygenase (1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), benzo[alpha]pyrene (benzpyrene), or a mixture of chlorinated biphenyls (Aroclor 1254)) exhibited marked elevation of 19-hydroxylation of PGE1, PGE2, PGA1, and PGA2 without affecting significantly 20-hydroxylation. However, with respect to effects on hydroxylation of a variety of xenobiotics, benzpyrene and Aroclor treatments differed markedly; whereas Aroclor treatment elevated the demethylation of ethylmorphine, benzphetamine, and p-chloro-N-methylaniline (PCMA), benzpyrene treatment had no effect on demethylation of ethylmorphine and only a marginal effect on that of PCMA. Both inducers elevated benzpyrene hydroxylation. By contrast, treatment with phenobarbital did not affect the hepatic microsomal PG's hydroxylation, although the hydroxylation of benzpyrene and the demethylation of ethylmorphine, benzphetamine, and PCMA were enhanced. Also, the hydroxylation of PG's by kidney cortex microsomes was not affected by either benzpyrene or Aroclor treatment. Inhibitors of monooxygenase were used to help delineate the type of monooxygenases induced. At low levels of alpha-naphthoflavone (ANF), benzpyrene hydroxylation in control- and Aroclor-treated guinea pigs was only little affected; by contrast, the same concentration of ANF markedly inhibited benzpyrene hydroxylation in benzpyrene-treated guinea pigs. On the other hand, metyrapone was most inhibitory in control guinea pigs. Support for the conclusion that benzpyrene induces in the guinea pig a hepatic monooxygenase with different characteristics than that found in control animals was provided by the observation that ANF (10 MICROM) inhibited PGE1 hydroxylation more pronouncedly in liver microsomes from benzpyrene-treated than from Aroclor-treated guinea pigs or controls. In addition, in benzpyrene and Aroclor-treated guinea pigs, ANF inhibited the (omega-1)-hydroxylation more pronouncedly than that of omega-hydroxylation. By contrast, metyrapone appeared to inhibit omega-hydroxylation more effectively than (omega-1)-hydroxylation. These results indicate that in the guinea pig, hydroxylation of PG's at the omega (20-) and omega-1 (19-) positions is catalyzed by different monooxygenases and that the inducers tested affect several hepatic monooxygenases with different specificities toward xenobiotics; however, with respect to PG's only the enzyme(s) involved in the 19-hydroxylation is affected.

Animals↗