Specific accumulation of CYP94A1 transcripts after exposure to gaseous benzaldehyde: induction of lauric acid ω-hydroxylase activity in Vicia sativa exposed to atmospheric pollutants.

The effects of air pollutants such as aldehydes, ozone, nitrogen dioxide and benzene on fatty acid ω-hydroxylase activity in Vicia sativa microsomes have been investigated. Four days old etiolated V. sativa seedlings were exposed to different concentrations of selected pollutants for varying exposure times. Growing etiolated V. sativa seedlings in air containing the gaseous benzaldehyde (150 nM) led to an 8-fold enhancement of lauric acid ω-hydroxylase activity in microsomes of treated plants compared to controls grown in pure air (96 ± 10 versus 12 ± 2 pmol/min/mg protein, respectively). The induction increased with increasing gas phase concentrations (10-1300 nM) and the maximum of activity was measured after 48 h of exposure. Northern blot analysis revealed that this induction occurred via transcriptional activation of the gene coding for CYP94A1. The absence of CYP94A2 and CYP94A3 transcription activation together with the missing effect on epoxide hydrolases activities indicate the specificity of CYP94A1 induction by benzaldehyde. Exposure to nitrogen dioxide, ozone and formaldehyde also stimulated lauric acid ω-hydroxylases activity while exposure to benzene did not show any effect.

Impaired locomotion and dopamine signaling in retinoid receptor mutant mice.

In the adult mouse, single and compound null mutations in the genes for retinoic acid receptor beta and retinoid X receptors beta and gamma resulted in locomotor defects related to dysfunction of the mesolimbic dopamine signaling pathway. Expression of the D1 and D2 receptors for dopamine was reduced in the ventral striatum of mutant mice, and the response of double null mutant mice to cocaine, which affects dopamine signaling in the mesolimbic system, was blunted. Thus, retinoid receptors are involved in the regulation of brain functions, and retinoic acid signaling defects may contribute to pathologies such as Parkinson's disease and schizophrenia.

Multiplicity generates diversity in the retinoic acid signalling pathways.

Complexity in the retinoid signalling system arises from a combination of several forms of retinoic acid, multiple cytoplasmic binding proteins and nuclear receptors, and the existence of polymorphic retinoic acid response elements. Additional diversity appears to be generated by heterodimeric interactions between two families of nuclear retinoic acid receptors, and between nuclear retinoic acid receptors and other members of the nuclear receptor superfamily. Thus, a complex array of combinatorial effects is beginning to emerge which may account for the pleiotropic effects of retinoids.

RXRalpha overexpression in cardiomyocytes causes dilated cardiomyopathy but fails to rescue myocardial hypoplasia in RXRalpha-null fetuses.

Retinoid X receptor alpha-null (RXRalpha-null) mutants exhibit hypoplasia of their ventricular myocardium and die at the fetal stage. In the present study, we wished to determine whether transgenic re-expression of RXRalpha in mutant cardiac myocytes could rescue these defects. Two transgenic mouse lines specifically overexpressing an RXRalpha protein in cardiomyocytes were generated, using the cardiac alpha-myosin heavy chain (alpha-MHC) promoter. Breeding the high copy number transgenic line onto an RXRalpha-null genetic background did not prevent the myocardial hypoplasia and fetal lethality associated with the RXRalpha(-/-) genotype, even though the transgene was expressed in the ventricles as early as 10. 5 days post-coitum. These data suggest that the RXRalpha function involved in myocardial growth may correspond to a non-cell-autonomous requirement forsignal orchestrating the growth and differentiation of myocytes. Interestingly, the adult transgenic mice developed a dilated cardiomyopathy, associated with myofibrillar abnormalities and specific deficiencies in respiratory chain complexes I and II, thus providing an additional model for this genetically complex disease.

Mobile phone-based surveillance of cardiac patients at home.

We tested the reliability, acceptability and feasibility of a home-monitoring system for cardiac patients. Each participant was equipped with a mobile phone, an automatic blood pressure device and a digital weight scale. In total, 20 patients (14 patients with chronic heart failure, six patients with hypertension; mean age 50 years, standard deviation [SD] 14) were monitored for 90 days each. They were asked to measure their blood pressure, pulse and body weight every day, and to transfer the data together with the dosage of medication to the telemonitoring server using wireless Internet technology in the mobile phone. The physician in charge received email alerts when reported data fell outside pre-defined limits. The patients' compliance with the system was high. During a cumulative monitoring period of 1,735 days, there were 2,040 data transfer sessions, a mean of 102 per patient (SD 43). The mean percentage of successful data transfers was 83% (SD 22). The stability of the telemonitoring system was 98%, meaning that patient data transfer was almost always possible. The accessibility of the secure web server for physicians was above 99%. The web-based home-monitoring system was reliable and easy to handle for both patients and health care professionals. It may be a useful tool for patients with heart failure as well as hypertensive patients.

Function of RARalpha during the maturation of neutrophils.

The retinoic acid receptor alpha gene is the target of chromosomal rearrangements in all cases of acute promyelocytic leukemia (APL). This recurrent involvement of RARalpha in the pathogenesis of APL is likely to reflect an important role played by this receptor during the differentiation of immature myeloid cells to neutrophils. RARalpha is a negative regulator of promyelocyte differentiation when not complexed with RA, and stimulates this differentiation when bound to RA. Since RARs are dispensable for the generation of mature neutrophils, their role thus appears to be to modulatory, rather than obligatory, for the control of neutrophil differentiation. In vitro, retinoic acid is also a potent inducer of neutrophil cell fate, suggesting that it might play a role in the commitment of pluripotent hematopoietic progenitors to the neutrophil lineage. Thus, the APL translocations target an important regulator of myeloid cell differentiation.

Absence of p53-dependent cell cycle regulation in pluripotent mouse cell lines.

We examined the expression of p53 in three lines of pluripotent embryonal carcinoma (EC) and ES cells. p53 mRNA and protein levels were constitutively high in two lines but absent from one. In the P19 line of EC cells neither p53 protein nor mRNA was detected. The first intron of the p53 gene in these cells had been invaded by a murine leukemia virus and there was extensive hypermethylation of the p53 gene accompanying its inactivation. In all three cell lines, irradiation resulted in arrest of the cells in the G2 but not in the G1 phase of the cell cycle despite the induction of p21cip1 in the cell lines expressing p53. Thus, the chromosomal stability of EC and ES cells appears to be not dependent on the p53 protein and we interpret our results to suggest that these cells may require the deletion of p53 dependent cell cycle regulation in order to become immortalized.

New potent alpha-glucohydrolase inhibitor MDL 73945 with long duration of action in rats.

Inhibition of intestinal alpha-glucohydrolase activity is one approach for reducing the glycemic response from dietary carbohydrate and may prove useful for the treatment of diabetes mellitus. In this article, we describe the pharmacological properties of a time-dependent intestinal alpha-glucohydrolase inhibitor, MDL 73945. When preincubated 2 h with a rat intestinal mucosa preparation before substrate addition, MDL 73945 was a potent inhibitor of sucrase, maltase, glucoamylase, and isomaltase activities (MDL 73945 concentrations required to cause a 50% decrease in enzyme activity, 2 x 10(-7), 1 x 10(-6), 5 x 10(-6), and 8 x 10(-6) M, respectively); without preincubation, it was 10- to 500-fold less potent. In rats, a single oral dose of MDL 73945 administered simultaneously with 2 g/kg body wt sucrose resulted in a dose-dependent reduction in the area under the 0- to 3-h glycemic response curve, which was significant at 1 (45% reduction) and 3 (65% reduction) mg/kg. When administered 1 h before sucrose, the compound was more potent, with 0.3 mg/kg MDL 73945 significantly reducing the glycemic response to sucrose by 62%. A reduction in the glycemic response to sucrose was accompanied by reduced insulin secretion. MDL 73945 was slightly less effective against a starch load, with 3 and 10 mg/kg MDL 73945 administered 0.5 h before starch reducing the glycemic response by 39 and 52%, respectively. MDL 73945 was more effective against a sucrose load in streptozocin-administered rats than in control rats and was as effective after 16 daily doses as after a single dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Developmental expression of murine retinoid X receptor (RXR) genes.

The developmental expression patterns of the three mouse retinoid X receptor genes (RXR alpha, beta and gamma) have been investigated by Northern blotting and in situ analysis of RNA transcript distribution, and compared to those of retinoic acid receptor (RAR) genes. RXR beta showed a diffuse and probably ubiquitous expression pattern at all developmental stages studied. RXR alpha also exhibited a diffuse expression at early developmental stages, but an enhanced in situ labelling was observed during late development in the epidermis and several other squamous epithelia. By contrast, RXR gamma apparently displayed a restricted expression in the myogenic lineage, i.e. in myotomes and subsequently in various differentiating muscles including those of the face and limbs. Apparently RXR gamma was not co-expressed with RAR beta and RAR gamma in these domains. RXR gamma transcripts were developmentally regulated in the otic epithelium, the retina, the pituitary and thyroid glands. In addition, RXR gamma was expressed in several discrete areas of the fetal central nervous system, namely in the diencephalon, the striatum and in part of the ventral horns of the spinal cord. In the two latter domains, there was a precise co-expression with RAR beta transcripts, although with quantitative differences, which suggests a possible preferential heterodimerization between these two retinoic acid receptors in the developing central nervous system.

Limited specificity and large overlap of the functions of the mouse RAR gamma 1 and RAR gamma 2 isoforms.

The RAR gamma gene generates two major isoforms, RAR gamma 1 and RAR gamma 2, which originate from two distinct promoters. We report here the engineering of mice lacking RAR gamma 1, but in which RAR gamma 2 is normally expressed. The effect of this null mutation has been compared with those previously described for RAR gamma 2 and all RAR gamma isoforms (total RAR gamma gene inactivation), both in single mutants and in double mutants bearing additional null mutations in their RAR alpha, RAR beta or RXR alpha genes. RAR gamma 1 mutants, but not RAR gamma 2 mutants, displayed a subset of the abnormalities exhibited by total RAR gamma null mutants (growth deficiency, abnormal cricoid cartilage and occasional cervical vertebra defects), suggesting that RAR gamma 1 is the main isoform mediating the corresponding RAR gamma functions. Interestingly, cricoid cartilage defects were also found in a fraction of heterozygote animals for the RAR gamma 1, RAR gamma or RAR alpha mutations, indicating that wild type levels of RARs are required for the normal morphogenesis of this structure. Compound RAR alpha/RAR gamma 1 and RAR alpha/RAR gamma 2 double null mutants exhibited only a small fraction of the defects found in RAR alpha/RAR gamma double null mutants. Moreover, these defects were often partially penetrant, or corresponded to a less severe form. However, they occurred preferentially in certain compound mutants, demonstrating that given isoforms mediate specific functions of RAR gamma in the context of a RAR alpha null background. In a RXR alpha null background, both RAR gamma 1 and gamma 2 isoform mutations resulted in increased severity of the RXR alpha null ocular phenotype. Together, the present observations indicate that the functions of the two RAR gamma isoforms overlap to a large extent, but also that each of these isoforms exhibits a limited functional specificity. Furthermore, the occurrence of morphological defects in heterozygote mutants for a single RAR isoform provides a basis for explaining the strong conservation of these isoforms during vertebrate evolution.

Transcriptional regulation of retinoic acid receptor beta in retinoic acid-sensitive and -resistant P19 embryocarcinoma cells.

As in other embryocarcinoma (EC) cell lines retinoic acid (RA) rapidly induces expression of the nuclear retinoic acid receptor (RAR) beta in murine P19 EC cells, while RAR alpha is expressed constitutively. In the RA-resistant P19 EC-derived RAC65 cells, however, there is no such induction and an aberrant (smaller) RAR alpha transcript is expressed. RAR gamma 1 is expressed at low levels in both cell lines. To study the regulation of the RAR beta gene and the possible involvement of RAR alpha protein in transcriptional activation of the RAR beta gene we transfected these cells with a construct containing a 1.6 kb promoter fragment of the human RAR beta gene fused to the CAT gene. Upon transient assays in P19 EC cells CAT activity is enhanced rapidly by RA, to more than 100-fold in a concentration-dependent fashion. On the contrary no activity can be observed in the RA-resistant RAC65 cells; however, co-transfection of hRAR alpha, hRAR beta or hRAR gamma 1 restores the RA-dependent induction of CAT activity. These results clearly show that RAR alpha and RAR gamma 1 can transactivate the RAR beta gene; that RAR beta can stimulate its own expression and that resistance to RA in RAC65 cells is probably due to the altered RAR alpha transcript present in these cells.

A retinoid acid 'resistant' t(15;17) acute promyelocytic leukemia cell line: isolation, morphological, immunological, and molecular features.

We report the isolation of a maturation-resistant acute promyelocytic leukemia (APL) cell line. This permanent cell line, derived from the same patient as the maturation inducible NB4 cell line, is the first retinoid-resistant cell line with a t(15;17) chromosomal translocation. Morphological, immunocytochemical and molecular features of the maturation responsive (NB4) and unresponsive (NB4-RAr) cells are compared. The isolation of the NB4-RAr cell line occurred through a two-step process requiring the continuous selective pressure of all-trans-retinoic acid. Cells are also resistant to 13-cis-retinoic acid. Karyotypic and Southern-blot analyses show that the two cell lines are similar with respect to the translocation. Northern-blot analyses show that the chimeric fusion transcript PML-RAR alpha and the normal allelic PML and RAR alpha transcripts are similarly expressed in both cell lines. The molecular basis for unresponsiveness to retinoic acid is not known. This resistant cell line offers a cellular model for molecular biology studies on the mechanism of induction of APL cell maturation, as well as a means to elucidate the molecular mechanisms of resistance. It also furnishes a unique tool for designing and/or screening new therapeutic drugs to avoid or relieve retinoid maturation blockage.

Roles of retinoic acid receptors and of Hox genes in the patterning of the teeth and of the jaw skeleton.

Retinoic acid receptors and transcriptional factors encoded by Hox genes play key roles in vertebrate development and belong to an integrated functional network. To investigate the actual functions of these molecules during ontogenesis and in particular in the patterning of the cranial neural crest cells giving rise to the teeth and to the jaw bones, we have generated null mutant mice lacking functional retinoic acid receptors or Hox genes by gene targeting in embryonic stem cells.

Evaluation of an Integrated Telemonitoring Surveillance System in Patients with Coronary Heart Disease.

OBJECTIVES: Cardiovascular diseases are the most frequent cause of death in industrialized countries. Non-adherence with prescribed medication and recommended lifestyle changes significantly increases the risk of major cardiovascular events. The telemonitoring programme MyCor (Myokardinfarkt und Koronarstent Programm in Tirol) is a multi-modal intervention programme to improve lifestyle and medication management of patients with coronary heart disease (CHD). It includes patient education, self-monitoring with goal-setting and feedback, and regular clinical visits. We evaluated the MyCor telemonitoring programme regarding technical feasibility, user acceptance, patient adherence, change in health status, and change in quality of life. METHODS: A 4½-month study was conducted with two telemonitoring phases and one interim phase. The study comprised patient surveys, standardized assessment of quality of life using the MacNew questionnaire at study entry and after 4 and 18 weeks, analysis of adherence to medication and physical activity during the two telemonitoring phases, and analysis of reached goals regarding health conditions during the telemonitoring phases. RESULTS: Twenty-five patients (mean age: 63 years) participated in the study. Patients showed a high acceptance of the MyCor telemonitoring programme. Patients reported feelings of self-control, motivation for lifestyle changes, and improved quality of life. Adherence to daily measurements was high with 86% and 77% in the two telemonitoring phases. Adherence to medication was also high with up to 87% and 80%. Pre-defined goals for physical activity were reached in up to 86% and 73% of days, respectively. Quality of life improved from 5.5 at study entry to 6.3 at the end (p< 0.01; MacNew questionnaire). Reductions in blood pressure and heart rate or an improvement in reaching defined goals could not be observed. CONCLUSIONS: The MyCor telemonitoring programme Tirol for CHD patients has a high rate of acceptance among included patients. Critical evaluation revealed subjective benefits regarding quality of life and health status as well as high adherence rates to medication and lifestyle changes. Achieving long-term adherence and verifying clinical outcomes, however, remains an open issue. Our findings will promote further studies, addressing different strategies for an optimal mix of patient education, telemonitoring, feedback, and clinical follow-ups.

IKZF1 deletion is an independent prognostic marker in childhood B-cell precursor acute lymphoblastic leukemia, and distinguishes patients benefiting from pulses during maintenance therapy: results of the EORTC Children's Leukemia Group study 58951.

The added value of IKZF1 gene deletion (IKZF1(del)) as a stratifying criterion in B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is still debated. We performed a comprehensive analysis of the impact of IKZF1(del) in a large cohort of children (n=1223) with BCR-ABL1-negative BCP-ALL treated in the EORTC-CLG trial 58951. Patients with IKZF1(del) had a lower 8-year event-free survival (EFS, 67.7% versus 86.5%; hazard ratio (HR)=2.41; 95% confidence interval (CI)=1.75-3.32; P<0.001). Importantly, despite association with high-risk features such as high minimal residual disease, IKZF1(del) remained significantly predictive in multivariate analyses. Analysis by genetic subtype showed that IKZF1(del) increased risk only in the high hyperdiploid ALLs (HR=2.57; 95% CI=1.19-5.55; P=0.013) and in 'B-other' ALLs, that is, lacking classifying genetic lesions (HR=2.22; 95% CI=1.45-3.39; P<0.001), the latter having then a dramatically low 8-year EFS (56.4; 95% CI=44.6-66.7). Among IKZF1(del)-positive patients randomized for vincristine-steroid pulses during maintenance, those receiving pulses had a significantly higher 8-year EFS (93.3; 95% CI=61.3-99.0 versus 42.1; 95% CI=20.4-62.5). Thus, IKZF1(del) retains independent prognostic significance in the context of current risk-adapted protocols, and is associated with a dismal outcome in 'B-other' ALL. Addition of vincristine-steroid pulses during maintenance may specifically benefit to IKZF1(del) patients in preventing relapses.

Both retinoic acid receptors alpha (RARalpha) and gamma (RARgamma) are able to initiate mouse upper-lip skin glandular metaplasia.

Embryonic mouse upper-lip skin explants treated with 16.7 microM all-trans retinoic acid (tRA) give rise to a glandular metaplasia of hair vibrissa follicles; however, at this concentration, tRA can activate not only the three retinoic acid receptors (RARalpha, beta, and gamma), but also the retinoid X receptors (RXRalpha, beta, and gamma) as a consequence of its isomerization to 9-cis retinoic acid. We therefore studied the respective roles of the RXR and RAR by treating RARalpha(-/-), beta(-/-), and gamma(-/-) skin explants with tRA and wild-type explants with synthetic retinoids specific for RXR or for each of the RAR. The null mutation of the RARalpha, RARbeta, and RARgamma genes did not prevent tRA-induced hair glandular metaplasia, but RARgamma inactivation dramatically reduced its ratio. As demonstrated by treating explants with a RAR- or a RXR-specific panagonist (CD367 and Ro25-7386, respectively), RAR are primarily responsible for this metaplasia. The use of two retinoids (Ro40-6055, 8 x 10(-3) microM, or CD437, 7.7 x 10(-2) microM) that are believed to act, respectively, as a RARalpha- or a RARgamma-specific agonist showed that both these receptors can initiate a metaplasia. In contrast, BMS453, a RARbeta-specific agonist, was unable to give rise to any metaplasia. Nevertheless, the highest degrees and ratios of metaplasia were only obtained after treatment with the CD367 RAR panagonist, or with either Ro40-6055 or CD437 at a concentration sufficient to allow the activation of the three RAR, suggesting that RARbeta activation is required for a metaplasia of all vibrissae.

Retinoic acid receptor gene expression in human skin.

Human skin exhibits a characteristic, pleiotypic response to topical retinoic acid. In attempting to understand this response at the molecular level, we have used fast protein liquid chromatography (FPLC) and RNA blot hybridization to characterize the expression of the nuclear retinoic acid receptor (RAR) alpha, beta, and gamma genes in adult human epidermis. Size exclusion FPLC of 0.6 M NaCl nuclear extracts prepared from keratome biopsies revealed two peaks of specific [3H] retinoic acid (RA) binding at Mr 45 and 18 kDa, in agreement with the expected sizes of RAR and cellular RA binding protein. Blot hybridization analysis of total RNA extracted from keratome biopsies revealed that RAR-gamma was the predominant RAR species expressed in human epidermis, as RAR-alpha transcripts were detectable only at low levels and RAR-beta transcripts were undetectable. RAR transcripts were not induced by topical treatment with 0.1% RA cream under occlusion for 4 h or 4 d. Moreover, there was no significant difference in RAR-gamma transcript levels in normal and psoriatic epidermis. RAR-gamma transcripts were constitutively expressed not only in cultured human keratinocytes, but also in human dermal and lung fibroblasts. RAR-beta was induced by RA in dermal fibroblasts, but not in keratinocytes. RA induced IL-1 beta transcripts in keratinocytes rapidly (2 to 4 h) and at low concentrations (3 x 10(-10) M), consistent with activation of the IL-1 beta gene via RAR. These results demonstrate constitutive expression of RAR-gamma in human epidermis, and suggest that RAR-gamma is a molecular target of RA action in adult human skin.

Differential regulation of retinoic acid receptors and binding proteins in human skin.

Many of the pleiotropic effects of retinoids are likely to be mediated by nuclear retinoic acid receptors (RAR) acting as ligand-dependent enhancer factors. However, in previous studies we have been unable to document altered RAR expression at the RNA level in response to retinoic acid (RA) treatment or in psoriatic lesions, conditions characterized by marked alterations in keratinocyte proliferation and differentiation, which are either caused by or responsive to RA. In an attempt to identify other potential regulators of RA responsiveness, we have used RNA blot hybridization to study the expression of the cellular retinoic acid binding proteins (CRABP) CRABP-I and CRABP-II, the RAR-gamma isoforms RAR-gamma 1 and RAR-gamma 2, and the low-affinity RAR homologue RXR in normal, RA-treated, and psoriatic human epidermis. CRABP-II is selectively and markedly induced by RA in adult human skin (J Biol Chem 266:17662-17666, 1991). However, in submerged, serum-free keratinocyte cultures, CRABP-II mRNA could not be induced by RA. Comparisons of intact human skin, submerged keratinocyte cultures, and human skin equivalent cultures indicated that induction of CRABP-II by RA requires epidermal stratification, dermal-epidermal interactions, or both. CRABP-II transcripts were also expressed in heat-separated human dermis at levels similar to those found in epidermal keratome biopsies, whereas CRABP-I transcripts were undetectable in dermal RNA. CRABP-II transcripts were markedly elevated in psoriatic lesions, as they were in RA-treated skin. In contrast, CRABP-I mRNA was undetectable and not increased in psoriatic lesions. Expression of RAR-gamma isoforms and RXR was not detectably altered in either psoriatic lesions or in RA-treated skin. Thus, altered expression of CRABP-II appears more likely to regulate the cutaneous actions of RA than does altered expression of CRABP-I, RXR, or RAR-gamma isoforms. From these and other results, a model for regulation of RA action involving sequestration of RA by CRABP-II is proposed.

Retinoic acid receptors and binding proteins in human skin.

Nuclear retinoic acid receptors (RAR) are likely to mediate many of the pleiotypic cutaneous actions of retinoids by acting as ligand-dependent enhancer factors. The presence of nuclear RAR in skin was confirmed by identification of a 45-kDa nuclear RA binding activity by fast protein liquid chromatography (FPLC). Analysis of RNA extracted from skin specimens demonstrated expression of RAR-alpha and RAR-gamma transcripts, as well as expression of the homologous low-affinity receptor, RXR-alpha. Both isoforms of RAR-gamma RAR-gamma 1 and RAR-gamma 2 were detectable, with RAR-gamma 1 being the more strongly expressed. FPLC analysis also demonstrated a 15-kDa peak of specific RA binding activity, consistent with the presence of cellular retinoic acid binding protein (CRABP). Of the two known forms of CRABP, CRABP-II was much more strongly expressed than CRABP-I at the level of steady-state mRNA. CRABP-II was also expressed in keratinocytes and fibroblasts in vitro. CRABP-II was up-regulated by agents that induce keratinocyte differentiation, and inhibited by prolonged exposure to high concentrations of RA. In contrast, CRABP-II was consistently induced by RA in dermal, but not in lung fibroblasts. CRABP-I was expressed at low to undetectable levels under all these conditions. The presence of tissue-specific and differentiation-related regulation of CRABP-II suggests that it may be an important regulator of RA action in human skin.

1-(Thienylalkyl)imidazole-2(3H)-thiones as potent competitive inhibitors of dopamine beta-hydroxylase.

1-(2-Thienylalkyl)imidazole-2(3H)-thiones (5a-k) are competitive inhibitors of dopamine beta-hydroxylase (DBH) and demonstrate the utility of thiophene in the design of potent competitive inhibitors of this enzyme. The structure-activity relationships for these compounds are discussed and compared with those of 1-phenylalkyl-imidazole-2(3H)-thiones (1). With the aid of molecular modeling, an idealized active-site conformer is proposed and an explanation for the difference in activity between the phenyl (1) and thienyl (5) DBH inhibitors is presented. The difference in activity is consistent with our proposal that thiophene may not always be a bioisostere for phenyl. The inhibitor of most interest, 1-[2-(2-thienyl)ethyl]imidazole-2(3H)-thione (5g), was selected for study in the spontaneously hypertensive rat. The changes in dopamine and norepinephrine levels that resulted from oral administration of 5g correlated with the reduction of blood pressure.