Familial influence and childhood trauma in female alcoholism.

BACKGROUND: To assess the role of genetic and environmental factors in female alcoholism using a large population-based twin sample, taking into account possible differences between early and late onset disease subtype. METHOD: Twins aged 20-47 years from the Swedish Twin Registry (n=24 119) answered questions to establish lifetime alcohol use disorders. Subjects with alcoholism were classified for subtype. Structural equation modeling was used to quantify the proportion of phenotypic variance due to genetic and environmental factors and test whether heritability in women differed from that in men. The association between childhood trauma and alcoholism was then examined in females, controlling for background familial factors. RESULTS: Lifetime prevalence of alcohol dependence was 4.9% in women and 8.6% in men. Overall, heritability for alcohol dependence was 55%, and did not differ significantly between men and women, although women had a significantly greater heritability for late onset (type I). Childhood physical trauma and sexual abuse had a stronger association with early onset compared to late onset alcoholism [odds ratio (OR) 2.54, 95% confidence interval (CI) 1.53-3.88 and OR 2.29, 95% CI 1.38-3.79 respectively]. Co-twin analysis indicated that familial factors largely accounted for the influence of physical trauma whereas the association with childhood sexual abuse reflected both familial and specific effects. CONCLUSIONS: Heritability of alcoholism in women is similar to that in men. Early onset alcoholism is strongly association with childhood trauma, which seems to be both a marker of familial background factors and a specific individual risk factor per se.

The myxoid liposarcoma FUS-DDIT3 fusion oncoprotein deregulates NF-kappaB target genes by interaction with NFKBIZ.

FUS (also called TLS), EWSR1 and TAF15 (also called TAF2N) are related genes involved in tumor type-specific fusion oncogenes in human malignancies. The FUS-DDIT3 fusion oncogene results from a t(12;16)(q13;p11) chromosome translocation and has a causative role in the initiation of myxoid/round cell liposarcomas (MLS/RCLS). The FUS-DDIT3 protein induces increased expression of the CAAT/enhancer-binding protein (C/EBP) and nuclear factor-kappaB (NF-kappaB)-controlled gene IL8, and the N-terminal FUS part is required for this activation. Chromatin immunoprecipitation analysis showed that FUS-DDIT3 binds the IL8 promoter. Expression studies of the IL8 promoter harboring a C/EBP-NF-kappaB composite site pinpointed the importance of NF-kappaB for IL8 expression in FUS-DDIT3-expressing cells. We therefore probed for possible interaction of FUS-DDIT3 with members of the NF-kappaB family. The nuclear factor NFKBIZ colocalizes with FUS-DDIT3 in nuclear structures, and immunoprecipitation experiments showed that FUS-DDIT3 binds the C-terminal of NFKBIZ. We also report that additional NF-kappaB-controlled genes are upregulated at the mRNA level in FUS-DDIT3-expressing cell lines and they can be induced by NFKBIZ. Taken together, the results indicate that FUS-DDIT3 deregulates some NF-kappaB-controlled genes through interactions with NFKBIZ. Similar mechanisms may be a part of the transformation process in other tumor types carrying FUS, EWSR1 and TAF15 containing fusion oncogenes.

Trends in long-term survival after myocardial infarction: less favourable patterns for patients from deprived areas.

OBJECTIVE: New treatments have improved the prognosis for patients with acute myocardial infarction. However, studies on long-term survival are not unequivocally in favour of an improved long-term prognosis. This study aimed to analyse trends in 3-year survival in relation to sex, age and socioeconomic level of residential area. SETTING: The Malmö myocardial infarction register, Sweden. PARTICIPANTS: All men and women in the city who, between 1978 and 1995, were admitted for a first acute myocardial infarction (n = 11 226). MAIN OUTCOME MEASURES: Age-standardized 3-year survival rates. RESULTS: Both 28-day and 3-year survival rates improved markedly during the study period. Age-standardized 3-year survival (per 100 patients) amongst men and women who survived 28 days increased, between 1978-81 and 1991-95, from 64 to 78 in men and from 66 to 77 in women, an annual increase of 1.4% (95% CI = 1.1-1.7) and 1.2% (0.8-1.5), respectively. There were marked differences in survival between residential areas with different socioeconomic circumstances. The 3-year survival rates amongst men correlated significantly with the socioeconomic circumstances in the areas expressed in terms of a socioeconomic score (men: r = 0.60, n = 17, P = 0.01; women: r = 0.37, P = 0.15). Trends tended to be less favourable in deprived areas. CONCLUSION: Three-year survival after first myocardial infarction has continuously improved for men and women in all age groups. Prognosis was worse and trends tended to be less favourable for patients from deprived areas.

Distribution and determinants of ischaemic heart disease in an urban population. A study from the myocardial infarction register in Malmö, Sweden.

OBJECTIVE: Age adjusted incidence of myocardial infarction has been found to vary substantially between the residential areas of the city of Malmö. The objective of this study was to assess the extent to which major biological risk factors and socio-economic circumstances account for the differences in incidence of and mortality from myocardial infarction. DESIGN: Ecological study of risk factor prevalence and incidence and mortality from myocardial infarction. SETTING: Seventeen administrative areas in Malmö, Sweden. SUBJECTS: Assessment of risk factor prevalence was based on 28 466 men and women, ranging from 45 to 73 years old, who were recruited as participants in the Malmö Diet and Cancer study. Information on serum lipids was available in a random subsample of 5362 subjects. Information about socio-economic level of the residential area was based on statistics from the Malmö City Council and Statistics Sweden. MAIN OUTCOME MEASURES: Weighted least square regressions between prevalence of risk factors (i.e. smoking, hypertension, obesity, diabetes, hypercholesterolemia and hypertriglyceridemia), a myocardial infarction risk score, a socio-economic score and incidence and mortality from myocardial infarction. RESULTS: The risk factor prevalence and myocardial infarction incidence was highest in areas with low socio-economic level. Prevalence of smoking, obesity and hypertension was significantly associated with myocardial infarction incidence and mortality rates amongst men (all r > 0.60). Prevalence of smoking was significantly associated with incidence and mortality from myocardial infarction amongst women (r = 0.66 and r = 0.61, respectively). A myocardial infarction risk score based on four biological risk factors explained 40-60% of the intra-urban geographical variation in myocardial infarction incidence and mortality. The socio-economic score added a further 2-16% to the explained variance. CONCLUSION: In an urban population with similar access to medical care, well-known biological cardiovascular risk factors account for a substantial proportion of the intra-urban geographical variation of incidence of and mortality from myocardial infarction. The socio-economic circumstances further contribute to the intra-urban variation in disease.

Three-year survival and recurrence after stroke in Malmö, Sweden: an analysis of stroke registry data.

BACKGROUND AND PURPOSE: Data from the Malmö Stroke Registry were analyzed to determine whether any change in survival or nonfatal stroke recurrence rates had occurred during the 4-year period from 1989 through 1992 and whether prognosis was related to area of residence. METHODS: The series comprised 2290 patients, 1051 men and 1239 women, followed up for 3 years after their first stroke during the period 1989 through 1992. RESULTS: Of the series as a whole, 959(43.4%) died and 137(6%) suffered a second nonfatal stroke. Multivariate analysis showed age, type of stroke, severity of stroke, and the presence of diabetes mellitus or cardiac disease each to be an independent predictor of mortality, and the presence of diabetes, atrial fibrillation, and history of transient ischemic attacks each to be associated with increased risk of recurrence. Treatment for hypertension was associated with a protective effect. As compared to those with first stroke in 1989, those with first stroke in 1992 were characterized by a lower recurrence rate, which was reduced by 70% in the male subgroup (P=0.003) and by 80% in the female subgroup (P=0.006), the corresponding reduction in all-cause mortality being 30% (P=0.007) and 10% (P=0.5, NS). Recurrence-free survival rates differed markedly between the 17 residential areas studied. CONCLUSIONS: The present study showed that survival rates after stroke have improved and recurrence rates have declined in this urban population. Further studies are needed to ascertain to what extent intraurban variation in the proportion of recurrence-free 3-year survivors is to be explained by differences in the severity of initial stroke and other prognostic markers, or in initial treatment and secondary preventive measures.

Adsorption of some technetium-99m radiopharmaceuticals onto disposable plastic syringes.

OBJECTIVE: The purpose of this study was to determine the adsorption behavior of some widely used, commercially available 99mTc radiopharmaceuticals onto different types of plastic syringes. METHODS: Kits were reconstituted with 99mTc-pertechnetate diluted with 0.9% saline to produce maximum radioactive concentrations, as stated by the manufacturers. Aliquots of the solutions were transferred to four different brands of 2-ml syringes. The activity in the syringes was measured before and after injections or simulated injections. The amount adsorbed to the plastic syringe barrel and plunger before and after washout also was measured at different time intervals. Comparisons between products from different manufacturers were made for 99mTc succimer (DMSA) and 99mTc macroaggregated albumin (MAA). RESULTS: Some 99mTC preparations undergo significant adsorption to plastic syringes. Adsorption differs considerably between products from different manufacturers. There was significantly higher residual activity in some types of syringes. In some cases the residual was as high as 40%-50% of the initial activity, and most of the adsorption occurred within 15 min of filling the syringe. CONCLUSION: The data suggest that the extent of adsorption depends on pharmaceutical excipients in the kits and/or the type of syringe used. When inappropriate syringes are used, the reduction in the administered activity may result in poor-quality images. Therefore, the compatibility between radiopharmaceutical and syringe should be investigated under normal conditions of preparation and use every time a new brand of syringe or a new radiopharmaceutical comes into use in diagnostic nuclear medicine.

How much can data on days with heavy drinking decrease the underestimation of true alcohol consumption?

An adjusted quantity-frequency method, with questions on occasions with heavy drinking, was used to estimate the consumption of alcohol during the last 30 days. The purpose was to analyze if it was possible to decrease the underestimation of true alcohol consumption. The questionnaire was mailed to a randomized sample of 1,500 individuals, 20-75 years of age, living in the city of Malmö, Sweden; 930 persons (64.3%) participated. Data on alcohol consumption were validated by comparison to sales of alcohol for the city of Malmö. The estimated per capita consumption of alcohol in the population was equivalent to 77.0% of the registered sale of alcohol in Malmö. By adding days with heavy drinking, the estimated weekly per capita consumption of alcohol among the alcohol consumers increased from 74.5 grams to 77.1 grams (+3.5%; p < .001). Of the alcohol consumers, 15.1% increased their reported consumption. In order to decrease even more the underestimation of the true alcohol consumption, we suggest the use of questions about any alcohol consumption that deviates from the typical consumption of each individual.

Antirepression function in Escherichia coli for the cAMP-cAMP receptor protein transcriptional activator.

The cAMP receptor protein (CRP) complex (cAMP-CRP) is a global regulator of gene expression. It influences transcription from a number of promoters in Escherichia coli, including two divergently oriented promoters in the pap pili-adhesin gene system. To further define the role of cAMP-CRP in pap regulation we monitored protein-DNA interactions in vitro and levels of pap transcription in vivo in wild-type and mutant pap-containing clones. The results showed that activation was mediated by a single cAMP-CRP-binding site centered at nucleotide positions -215.5 and -115.5 relative to the transcriptional start points. A target for the pap-specific regulatory protein PapB was localized adjacent to the cAMP-CRP-binding site. The long-range effects exerted from the protein-binding sites were consistent with the idea that cAMP-CRP caused a change in the local DNA conformation and that a nucleoprotein complex (involving cAMP-CRP and PapB) was formed in the region between the pap promoters. Moreover, transcription became independent of activation of cAMP-CRP and the PapB protein in a mutant lacking the nucleoid-associated protein H-NS. Our findings suggest that the cAMP-CRP complex mediates its positive regulatory function by alleviating transcriptional silencing and, as such, plays a role as antirepressor.

Transcriptional silencing and thermoregulation of gene expression in Escherichia coli.

Expression of specific adhesive properties by bacteria in general seems to be regulated to fit the environmental conditions. An example is the transcriptional regulation of digalactoside-specific binding by uropathogenic strains of Escherichia coli. The fimbrial structures (pili) on the bacterial surface carry the adhesin and are present during growth at 37 degrees C but are not produced by cells at lower temperatures, such as 25 degrees C. Thermoregulation of expression is due to temperature-dependent transcription of a regulatory cistron in the pilus-adhesin gene cluster. We have now identified and characterized a new regulatory locus (drdX) and show that a histone-like bacterial protein has an important role in this novel example of thermoregulation of transcription.

Upstream activating sequences that are shared by two divergently transcribed operons mediate cAMP-CRP regulation of pilus-adhesin in Escherichia coli.

Transcription of the genes encoding pilus-adhesin of serotype F13 in digalactoside-binding Escherichia coli required activation by the cAMP-CRP complex. Analysis of protein-DNA interaction in vitro showed that CRP bound in a cAMP-dependent manner to a sequence located 0.2 kb upstream of the point of transcription initiation of the pilus subunit operon. The cAMP-CRP activation included, in addition to the main pilus operon, the oppositely oriented operon encoding the Papl regulatory protein. Furthermore, the auto-regulatory product of the promoter-proximal gene (papB) in the pilus subunit operon was found to stimulate the papl transcriptional unit. Thus the cAMP-CRP complex and PapB might act in concert and indirectly promote pili synthesis by stimulating expression of the Papl positive regulator. The results of trans-complementation experiments and analyses using lacZ operon fusion derivatives showed that the cAMP-CRP activation also operated directly in cis on the pilus subunit operon. The region containing the CRP binding site appeared to function as an upstream activating sequence since deletion abolished expression even when the pap regulatory proteins Papl and PapB were supplied in trans. The implications for possible mechanisms of transcriptional activation by the cAMP-CRP complex at this novel location between the two oppositely oriented operons are discussed.

Autoregulation and multiple DNA interactions by a transcriptional regulatory protein in E. coli pili biogenesis.

An operon mediating biogenesis of digalactoside-binding pilus-adhesin of serotype F13 in uropathogenic Escherichia coli includes the regulatory gene papB. The papB gene product was found to act as transcriptional activator of an operon which includes the papB gene and several pap cistrons encoding the proteins of the pilus polymer. Studies of how pap gene expression was affected by increasing amounts of PapB protein in the cells showed that high levels did not stimulate transcription but caused repression. Results from in vitro studies demonstrated that the PapB protein was a sequence-specific DNA-binding protein. Binding studies using gel mobility shift assays and DNase I protection (footprinting) showed that PapB protein binds to three separate sites. A sequence greater than 200 bp upstream of the promoter, and directly adjacent to a binding site for the cAMP receptor protein-cAMP complex, appeared as a preferential PapB binding site. A second site was localized to sequences overlapping the -10 region of the promoter and a third binding site was found within the coding sequence of the papB gene itself. The data suggest that the PapB protein has a dual function as activator/repressor of pilus-adhesin transcription and that its autoregulatory mode of action involves differential binding to separate sites.

Regulatory genes in the thermoregulation of Escherichia coli pili gene transcription.

Expression of several different pilus adhesins by Escherichia coli is subject to thermoregulation. The surface-located fimbrial structures are present during growth at 37 degrees C but are not produced by cells grown at lower temperatures, such as 25 degrees C. As a step toward understanding the molecular mechanism, we have studied the role of different cistrons of a cloned pilus adhesin gene cluster (pap) from a uropathogenic E. coli isolate. By promoter cloning, mRNA analysis, and expression of subcloned genes in trans, we have identified the papI gene as the mediator of thermoregulation at the level of pilus adhesin gene transcription. Expression of the major pilus subunit gene (papA) and several other pilus protein cistrons appeared to be dependent on stimulation by the papB and papI gene products. Constructs carrying different pap DNA regions indicated that none of the known Pap proteins acts directly as thermosensor. The chromosomal rpoH gene and RpoH sigma factor did not appear to be required for pap transcription, and the thermoregulation of pilus gene transcription must be different from that of the heat shock regulon. By overexpressing the papI gene product from an expression plasmid in trans, we could circumvent the temperature regulation and turn on production of pilus adhesin at low temperature. Our results suggest that the level of mRNA encoding the PapI activator is limiting at low growth temperatures and that thermoregulation is due to a determinant in the papI-papB intercistronic region.

Functional and structural homology among regulatory cistrons of pili-adhesin determinants in Escherichia coli.

Expression of the digalactoside-binding Pap pili involves two trans-acting regulatory genes, papB and papI. Using pap-lac operon fusions and DNA hybridization probes derived from pap DNA we tested whether or not other pili-adhesin determinants from different Escherichia coli strains encode homologs to the pap regulatory genes. Digalactoside-specific clones of serotypes F72 and F11 complemented papB and papI mutants of the Pap (serotype F13) clone and DNA hybridization analysis showed that the clones are homologous in the DNA sequences encoding the two regulatory genes. Similar results were obtained with an S-pili determinant which mediates binding to sialic acid-containing receptors and the findings suggest that the regulatory regions may be more conserved than other genes in different pili-adhesin gene clusters. Determinants for type 1-pili (mannose-specific binding) and for pili associated with enterotoxigenic E. coli (K88, K99, CFAI, CFAII) did not appear to contain DNA sequences homologous to papB or papI. E. coli strain J96, which was the origin of the pap DNA, was found to carry two additional copies of papB-papI homologous sequences in the chromosome. In strains expressing more than one kind of pili the trans-active gene products thereby may allow for regulatory interaction between separate pili-adhesin gene systems.

Processed mRNA with differential stability in the regulation of E. coli pilin gene expression.

E. coli expressing the papA-I genes produce pili that mediate specific adhesion to mammalian cells. We show that the major pilus subunit gene, papA, is part of a polycistronic transcriptional unit subject to specific posttranscriptional processing. A primary transcript also encoding the papB regulatory gene product is endonucleolytically cleaved, resulting in the rapid decay of the papB-encoding 5' half of the mRNA, whereas the papA-encoding 3' half remains as a quite stable transcript. Processing and differential mRNA stability thereby result in accumulation of mRNAs encoding only the major pilus subunit. A sequence immediately downstream of the papA coding region may serve as a stability determinant for the papA transcript and concomitantly attenuate read-through transcription into the minor pilus subunit gene papH. This suggests that differential expression of genes within an operon may include endo- and exonucleolytic processing of the mRNA.

Oxidation of tricyclic antidepressant drugs, debrisoquine and 7-ethoxyresorufin, by human liver preparations.

Data obtained from human studies in vivo show that the dispositions of the tricyclic antidepressant drugs desmethylimipramine (DMI) and nortriptyline are related to the debrisoquine hydroxylation phenotype. To obtain insight into the enzymic mechanisms behind this, the metabolism of debrisoquine and antidepressant drugs by human liver preparations have been studied. The 2-hydroxylation of DMI in vitro correlates with the 4-hydroxylation of debrisoquine among various livers (rs = 0.90). Debrisoquine inhibits DMI hydroxylation competitively, and DMI inhibits debrisoquine hydroxylation, suggesting that DMI hydroxylation is catalysed by the debrisoquine hydroxylase in human liver. By monitoring the hydroxylation of DMI in various fractions during separation and purification of cytochrome P-450 from human liver microsomes we have purified a cytochrome P-450 which efficiently hydroxylates this drug. The apparently electrophoretically homogeneous enzyme had a molecular weight of 51,500 and hydroxylated DMI and debrisoquine at rates of up to 0.95 and 0.45 nmol/min . nmol P-450, respectively. This is probably the major debrisoquine hydroxylating cytochrome P-450 in man. Nortriptyline 10-hydroxylation correlates strongly (r = 0.96) with debrisoquine hydroxylation in human liver microsomes. Nortriptyline inhibits DMI-hydroxylation competitively, and the drug also inhibits the 4-hydroxylation of debrisoquine. Thus it is probable that nortriptyline is hydroxylated by debrisoquine hydroxylase. Imipramine N-demethylation did not correlate significantly (P greater than 0.1) with debrisoquine hydroxylation among microsomes from nine livers. However, if a liver from a subject, which was a poor metabolizer of debrisoquine in vivo, was included, a correlation was obtained (r = 0.79, P less than 0.01, N = 10). Imipramine demethylation also correlated with DMI-hydroxylation only if the 'poor metabolizer' liver was included (r = 0.75, P less than 0.05, N = 10). Debrisoquine inhibited imipramine demethylation competitively. The data indicate that imipramine can interact with debrisoquine- and DMI-hydroxylase, but it is uncertain if this enzyme plays an important quantitative role in its demethylation. Ethoxyresorufin O-deethylation correlated with DMI hydroxylation (r = 0.80) in human liver preparations, and DMI inhibited the former reaction in what is probably a mixed competitive-non-competitive inhibition. Liver preparations from a subject who was a poor oxidizer of debrisoquine both in vivo and in vitro had unusually low capacity to metabolize ethoxyresorufin. Thus ethoxyresorufin, at least partly, seems to interact with an enzyme that can metabolize DMI in human liver.(ABSTRACT TRUNCATED AT 400 WORDS)

Overproduction and purification of the B2 subunit of ribonucleotide reductase from Escherichia coli.

The nrdB gene of Escherichia coli, coding for the B2 protein of ribonucleotide reductase, has been cloned in a runaway-replication vector. The runaway derivative pBEU17 carries the promoter-proximal portion of the E. coli alanyl-tRNA synthetase gene and proved useful for expressing cloned genes lacking their native transcription initiation signals. The alaS promoter is located approximately 500 base pairs upstream of a single BamHI restriction endonuclease cleavage site utilized in the construction of an expression recombinant plasmid, pBS1, for the nrdB product. After 5-h thermal induction of cells carrying the runaway recombinant pBS1, protein B2 constituted 40% of the soluble protein fraction of the cells. The high concentration of protein B2 in crude extracts of induced cells has enabled a simplified purification scheme to be developed for production of homogeneous and concentrated B2 preparations. Protein B2 produced from pBS1 is identical to the chromosomally encoded nrdB product of E. coli as regards molecular mass on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, enzyme activity, tyrosine radical content, and structure of the binuclear iron center. Amino acid sequence analysis showed that the two polypeptide chains of protein B2 are identical. They start with an alanine residue, and the first 30 residues confirmed the amino acid sequence predicted from the nucleotide sequence of the nrdB gene, apart from an NH2-terminal processing removal of the initiator methionine.

Transcriptional activation of a pap pilus virulence operon from uropathogenic Escherichia coli.

A gene cluster mediating production of pili in uropathogenic Escherichia coli was analysed with respect to regulation of pili synthesis. Two cistrons, papB and papI, were localized upstream of the major pilus subunit gene, papA. The papI-papB-papA region was characterized by nucleotide sequencing and by transcriptional analysis. The papA gene was primarily represented by an 800 nucleotide long transcript but was also co-transcribed with papB as a less abundant 1300 nucleotide long mRNA. Both transcripts presumably terminated at the same site downstream of the papA coding sequence. The weakly expressed papI gene was transcribed in the opposite direction to that of papB and papA. Studies with lacZ operon fusions showed that the papB gene encoded a trans-active effector required for papA transcription. Similarly, the papI gene stimulated papB transcription in trans. Furthermore, full expression of papA was cis dependent upon the papI-papB region. Transcription of the papB gene was shown to be dependent upon cAMP and its receptor protein. A binding site for the cAMP-CRP complex was postulated in the DNA sequence upstream of the papB promoter.

Cryptic plasmid of Neisseria gonorrhoeae: complete nucleotide sequence and genetic organization.

The naturally occurring cryptic plasmid pJD1 of Neisseria gonorrhoeae is 4,207 base pairs long and is found in about 96% of gonococcal strains. The total probable coding capacity of pJD1 was determined from the complete nucleotide sequence by using computational probes to identify open reading frames with similar codon usage and by screening for the presence of ribosomal binding sites before the start codons. Candidates for promoters and terminators were also found in the sequence. Based on these findings, we propose a model for the genetic organization of the plasmid. The model predicts two transcriptional units, each composed of five compactly spaced genes. A promoter of one of the transcripts was shown to function in Escherichia coli, and the products of three of the five genes in this operon were identified in minicell expression experiments. Of these, the cppA gene encoded a 9-kilodalton protein, and the cppB and cppC genes both coded for 24-kilodalton proteins. No expression of the other transcriptional unit was detected, but two genes in this operon were expressed in minicells when transcribed from an E. coli promoter. The experimental data were consistent with the model.

Inhibition of desmethylimipramine 2-hydroxylation by drugs in human liver microsomes.

The 2-hydroxylation of desmethylimipramine (DMI) correlates strongly with the 4-hydroxylation of debrisoquine (D) both in human volunteers and in vitro comparing human liver microsomes from different individuals. D competitively inhibits the 2-hydroxylation of DMI in vitro suggesting that DMI is hydroxylated by the 'debrisoquine hydroxylase' which is under monogenic control in man. We have characterized the effect of drugs on the hydroxylation of DMI in human liver microsomes by measuring the formation of 2-OH-DMI with HPLC using fluorescence detection. Amitriptyline, nortriptyline and metoprolol inhibited the hydroxylation of DMI competitively indicating interaction with the catalytical site for DMI 2-hydroxylation. Antipyrine and amylobarbitone at concentrations similar to their Km-values for metabolism did not inhibit DMI-hydroxylation. Thus, for these compounds there was a good correspondence between the drugs' capacity to inhibit DMI 2-hydroxylation competitively in vitro and their apparent metabolism by the 'debrisoquine hydroxylase' in vivo in man. Thioridazine, chlorpromazine, quinidine and quinine also inhibited DMI-hydroxylation competitively. Thioridazine was an unusually potent inhibitor (apparent inhibition constant Ki = 0.75 microM). Quinidine was also an unusually potent inhibitor (Ki = 0.27 microM) and much more efficient than its isomer quinine (Ki = 12 microM). Theophylline could inhibit DMI hydroxylation but with atypical kinetics. We suggest that this simple DMI in vitro test as well as earlier described inhibition tests with debrisoquine, sparteine and bufuralol can be used to screen if drugs interact with the 'debrisoquine hydroxylase' in human liver.