Evaluation of potential novel variations and their interactions related to bipolar disorders: analysis of genome-wide association study data.

BACKGROUND: Multifactor dimensionality reduction (MDR) is a nonparametric approach that can be used to detect relevant interactions between single-nucleotide polymorphisms (SNPs). The aim of this study was to build the best genomic model based on SNP associations and to identify candidate polymorphisms that are the underlying molecular basis of the bipolar disorders. METHODS: This study was performed on Whole-Genome Association Study of Bipolar Disorder (dbGaP [database of Genotypes and Phenotypes] study accession number: phs000017.v3.p1) data. After preprocessing of the genotyping data, three classification-based data mining methods (ie, random forest, naïve Bayes, and k-nearest neighbor) were performed. Additionally, as a nonparametric, model-free approach, the MDR method was used to evaluate the SNP profiles. The validity of these methods was evaluated using true classification rate, recall (sensitivity), precision (positive predictive value), and F-measure. RESULTS: Random forests, naïve Bayes, and k-nearest neighbors identified 16, 13, and ten candidate SNPs, respectively. Surprisingly, the top six SNPs were reported by all three methods. Random forests and k-nearest neighbors were more successful than naïve Bayes, with recall values >0.95. On the other hand, MDR generated a model with comparable predictive performance based on five SNPs. Although different SNP profiles were identified in MDR compared to the classification-based models, all models mapped SNPs to the DOCK10 gene. CONCLUSION: Three classification-based data mining approaches, random forests, naïve Bayes, and k-nearest neighbors, have prioritized similar SNP profiles as predictors of bipolar disorders, in contrast to MDR, which has found different SNPs through analysis of two-way and three-way interactions. The reduced number of associated SNPs discovered by MDR, without loss in the classification performance, would facilitate validation studies and decision support models, and would reduce the cost to develop predictive and diagnostic tests. Nevertheless, we need to emphasize that translation of genomic models to the clinical setting requires models with higher classification performance.

A Rare Reason of Hyperinsulinism: Munchausen Syndrome by Proxy.

Hyperinsulinism, one of the most important causes of hypoglycaemia, can be congenital or acquired. Rarely, drug toxicity can be a reason for hyperinsulinism. In the context of Munchausen syndrome by proxy (MSP), toxicity usually occurs in children due to drug administration by a parent or caregiver. A 7-year-old girl was referred to our department due to a hyperglycaemic period and hypoglycaemic episodes. On admission, gliclazide was initiated due to her hyperglycaemia, which we attributed to maturity onset diabetes of the young. However, during follow-up, hypoglycaemic levels were detected. Despite cessation of gliclazide, hypoglycaemic seizures occurred. Even with the medications administered, hypoglycaemia could not be prevented. During follow-up, the mother's affect, characterized by anxiety and interest in her daughter's medical care, appeared discordant with the situation. Due to our suspicion of MSP, we discovered toxic levels of gliclazide in the blood and urine samples which had been sent to the toxicology laboratory to search for hypoglycaemic agents. The patient was isolated, and all medications were stopped. After isolation, her hypoglycaemia disappeared, and she became hyperglycaemic (250 mg/dl). Physicians should consider the possibility of MSP in hyperinsulinaemic patients with discordant laboratory results and clinical symptoms, even if the child's parents display great concern.

Pediatric reference intervals for plasma and urine essential amino acids in a Turkish population.

AIM: To establish age- and sex-specific reference intervals for essential amino acids in a healthy Turkish pediatric population. MATERIALS AND METHODS: A total of 945 clinically healthy children (531 boys and 414 girls, ranging in age from birth to 14 years) were enrolled. Plasma and urine amino acids' concentrations were measured by high-performance liquid chromatography. RESULTS: Concentrations of essential amino acids in plasma were higher in girls than in boys in the age groups of 0-1 months and 7-14 years; however, there was no difference in the other age groups. Concentrations of essential amino acids in urine were higher in girls than in boys in the age group of 0-1 months; however, there was no difference in the other age groups. Our results demonstrated the sex-related differences in concentrations ofleucine, isoleucine, valine, phenylalanine, lysine, and histidine in plasma, which increased with age in boys but not in girls. The concentrations of leucine, tryptophan, methionine, and lysine in urine declined with age in girls but not in boys, which were sex-related differences, too. CONCLUSION: We defined essential amino acids' reference intervals in a Turkish pediatric population.

Discovering missing heritability and early risk prediction for type 2 diabetes: a new perspective for genome-wide association study analysis with the Nurses' Health Study and the Health Professionals' Follow-Up Study.

BACKGROUND/AIM: Despite the rise in type 2 diabetes prevalence worldwide, we do not have a method for early risk prediction. The predictive ability of genetic models has been found to be little or negligible so far. In this study, we aimed to develop a better early risk prediction method for type 2 diabetes. MATERIALS AND METHODS: We used phenotypic and genotypic data from the Nurses' Health Study and Health Professionals' Follow-up Study cohorts and analyzed them by using binary logistic regression. RESULTS: Phenotypic variables yielded 70.7% overall correctness and an area under the curve (AUC) of 0.77. With regard to genotype, 798 single nucleotide polymorphisms with P-values of lower than 1.0E-3 yielded 90.0% correctness and an AUC of 0.965. This is the highest score in the literature, even including the scores obtained with phenotypic variables. The additive contributions of phenotype and genotype increased the overall correctness to 92.9% and the AUC to 0.980. CONCLUSION: Our results showed that genotype could be used to obtain a higher score, which could enable early risk prediction. These findings present new possibilities for genome-wide association study analysis in terms of discovering missing heritability. These results should be confirmed by follow-up studies.

Simultaneous determination of cyclosporine A, tacrolimus, sirolimus, and everolimus in whole-blood samples by LC-MS/MS.

OBJECTIVES: Cyclosporine A (CyA), tacrolimus (TRL), sirolimus (SIR), and everolimus (RAD) are immunosuppressive drugs frequently used in organ transplantation. Our aim was to confirm a robust sensitive and selective liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for determination of CyA, TRL, SIR, and RAD in whole-blood samples. MATERIALS AND METHODS: We used an integrated online solid-phase extraction-LC-MS/MS system and atmospheric pressure ionization tandem mass spectrometry (API-MS/MS) in the multiple reaction monitoring (MRM) detection mode. CyA, TRL, SIR, and RAD were simultaneously analyzed in whole blood treated with precipitation reagent taken from transplant patients. RESULTS: System performance parameters were suitable for using this method as a high-throughput technique in clinical practice. The high concentration of one analyte in the sample did not affect the concentration of other analytes. Total analytical time was 2.5 min, and retention times of all analytes were shorter than 2 minutes. CONCLUSION: This LC-MS/MS method can be preferable for therapeutic drug monitoring of these immunosuppressive drugs (CyA, TRL, SRL, and RAD) in whole blood. Sample preparation was too short and simple in this method, and it permits robust, rapid, sensitive, selective, and simultaneous determination of these drugs.

The efficiency of proanthocyanidin in an experimental pulmonary fibrosis model: comparison with taurine.

Pulmonary fibrosis (PF) is a progressive fatal disorder. Bleomycin (BLM) is a widely used chemotherapeutic agent causing PF. Numerous agents have been investigated to prevent the progression of PF so far, but there is still a need to find more efficacious agents. Proanthocyanidin (PA) is a strong antioxidant, the main ingredient of grape seed extract. Since PA is ready for use in practice, we aimed to compare the preventive effect of PA in comparison with taurine (Tau) in BLM-induced PF. Forty Wistar male albino rats were used in the study and were divided into four groups: group 1, control; group 2, BLM-induced PF group; group 3, BLM-induced PF and treated with PA group; and group 4, BLM-induced PF and treated with Tau group. Treatments were begun 10 days before and continued 21 days after BLM injection. PA and Tau effectively inhibited inflammation, edema, severity of fibrosis, fibrosis extension, inflammatory cell accumulation, iNOS staining, and hydroxyproline level as well (p < 0.05). Total histological scores of the PA group were similar to the control group; Tau was significantly higher than the control group but lower than the BLM group (p < 0.05). We believe that PA could be a new treatment choice for PF, but further studies need to be conducted to verify the findings of the current study.

Detection of PIGO-deficient cells using proaerolysin: a valuable tool to investigate mechanisms of mutagenesis in the DT40 cell system.

While isogenic DT40 cell lines deficient in DNA repair pathways are a great tool to understand the DNA damage response to genotoxic agents by a comparison of cell toxicity in mutants and parental DT40 cells, no convenient mutation assay for mutagens currently exists for this reverse-genetic system. Here we establish a proaerolysin (PA) selection-based mutation assay in DT40 cells to identify glycosylphosphatidylinositol (GPI)-anchor deficient cells. Using PA, we detected an increase in the number of PA-resistant DT40 cells exposed to MMS for 24 hours followed by a 5-day period of phenotype expression. GPI anchor synthesis is catalyzed by a series of phosphatidylinositol glycan complementation groups (PIGs). The PIG-O gene is on the sex chromosome (Chromosome Z) in chicken cells and is critical for GPI anchor synthesis at the intermediate step. Among all the mutations detected in the sequence levels observed in DT40 cells exposed to MMS at 100 µM, we identified that ∼55% of the mutations are located at A:T sites with a high frequency of A to T transversion mutations. In contrast, we observed no transition mutations out of 18 mutations. This novel assay for DT40 cells provides a valuable tool to investigate the mode of action of mutations caused by reactive agents using a series of isogenic mutant DT40 cells.

The protective effects of ozone therapy in a rat model of acetaminophen-induced liver injury.

OBJECTIVES: Acetaminophen (APAP) overdose may cause acute liver injury. Ozone therapy (OT) is shown to reduce inflammation and necrosis in several entities. Thus, we have designed this study to evaluate the efficacy of OT in a rat model of APAP-induced liver injury. METHODS: Twenty-seven Sprague-Dawley rats were divided into three groups: sham, APAP and APAP+OT groups. In the APAP and the APAP+OT groups, liver injury was induced by oral administration of 1 g/kg APAP. The APAP+OT group received a single dose ozone/oxygen mixture (0.7 mg/kg) intraperitoneally 1h after APAP administration. All animals were killed at 24 hour after APAP administration. Blood samples and liver tissues were harvested to determine liver injury and oxidative stress parameters. Liver tissues and blood samples were obtained for biochemical and histopathological analyses. RESULTS: APAP administration caused necrosis in the liver after 24h. The degrees of liver necrosis of the APAP group were higher than the other groups (in both p<0.05, respectively). In the APAP+OT group, liver antioxidant enzymes activities were significantly higher than the APAP group (p<0.05), but were lower than the sham group (p<0.05). In the sham group, serum neopterin, a marker of cell-mediated immunity, concentrations (4.8±1.2 nmol/L) were lower than the APAP (14.7±1.4 nmol/L) and APAP+OT groups (7.5±2.4 nmol/L) (in both p<0.05, respectively). CONCLUSION: Our results showed that OT prevented liver necrosis in rats and reduced neopterin levels. These findings suggest that the use of OT as an adjuvant therapy which might improve the outcome in APAP induced liver injury.

Formation of hydroxymethyl DNA adducts in rats orally exposed to stable isotope labeled methanol.

Methanol is a large volume industrial chemical and widely used solvent and fuel additive. Methanol's well known toxicity and use in a wide spectrum of applications has raised long-standing environmental issues over its safety, including its carcinogenicity. Methanol has not been listed as a carcinogen by any regulatory agency; however, there are debates about its carcinogenic potential. Formaldehyde, a metabolite of methanol, has been proposed to be responsible for the carcinogenesis of methanol. Formaldehyde is a known carcinogen and actively targets DNA and protein, causing diverse DNA and protein damage. However, formaldehyde-induced DNA adducts arising from the metabolism of methanol have not been reported previously, largely due to the absence of suitable DNA biomarkers and the inability to differentiate what was due to methanol compared with the substantial background of endogenous formaldehyde. Recently, we developed a unique approach combining highly sensitive liquid chromatography-mass spectrometry methods and exposure to stable isotope labeled chemicals to simultaneously quantify formaldehyde-specific endogenous and exogenous DNA adducts. In this study, rats were exposed daily to 500 or 2000 mg/kg [¹³CD4]-methanol by gavage for 5 days. Our data demonstrate that labeled formaldehyde arising from [¹³CD4]-methanol induced hydroxymethyl DNA adducts in multiple tissues in a dose-dependent manner. The results also demonstrated that the number of exogenous DNA adducts was lower than the number of endogenous hydroxymethyl DNA adducts in all tissues of rats administered 500 mg/kg per day for 5 days, a lethal dose to humans, even after incorporating an average factor of 4 for reduced metabolism due to isotope effects of deuterium-labeled methanol into account.

Systemic and spinal administration of etanercept, a tumor necrosis factor alpha inhibitor, blocks tactile allodynia in diabetic mice.

Painful diabetic neuropathy is one of the most common forms of neuropathic pain syndromes. Tumor necrosis factor alpha (TNF-alpha) is a proinflammatory cytokine that has been implicated as a key pain mediator in the development and maintenance of neuropathic pain conditions. Recent studies showed that endogenous TNF-alpha production was also accelerated in neural tissues and spinal cord under chronic hyperglycemia. Thus, in this study, we investigated whether pharmacological inhibition of TNF-alpha by etanercept, a TNF-alpha antagonist, could block behavioral sign of diabetic neuropathic pain. Diabetes was induced by streptozotocin (STZ) (200 mg/kg, i.p.) in Balb-c mice and behavioral tests were performed between 45 and 60 days after STZ administration. Mechanical and thermal sensitivities were measured by a series of calibrated Von Frey filaments and hot plate test, respectively. Etanercept was given by either intravenous (i.v.), intrathecal (i.th.) or intraplantar (i.pl.) routes to the diabetic mice. Tactile allodynia, but not thermal hyperalgesia, developed in diabetic mice. Both i.v. (1, 10 and 20 mg/kg) or i.th. (1, 5 and 10 µg/mouse) treatments with etanercept produced dose dependent reversal of tactile allodynia in diabetic mice. However, etanercept was found to be inactive against allodynia when given i.pl. (1, 5 and 10 µg/mouse). Our results suggest that etanercept has promising effects on diabetic neuropathic pain with antiallodynic effects when given systemically or intrathecally.

Investigation of vasoactive ion content of herbs used in hemorrhoid treatment in Turkey.

OBJECTIVES: The aim of the present study is to determine anion and cation contents of the herbals used in Turkish folk remedy to explore the rationale of their use in hemorrhoid treatment in the context of the vasoactivity of these elements. DESIGN: Herbs used in the treatment of hemorrhoid were determined by the way of literature search. These herbs were obtained from certified herb sellers. Ground herb samples were placed in individual tubes containing methanol and incubated for 48 hours at 30 degrees C. At the end of the incubation, supernatants were analyzed for their ion concentrations by using ion chromatography. RESULTS: The difference between ion levels between systemic and locally used herbs, was not statistically significant (p>0.05). Anion concentrations (except nitrate) of locally used herbs were slightly higher than systemically used herbs (p>0.05). Cation levels (except magnesium) of systemically used herbs were slightly higher than locally used herbs (p>0.05). It was shown that the concentration of vasoconstrictor effective ions was higher than the concentration of vasodilator effective ions (p<0.001). While vasoconstrictor ion concentration of systemically used herbs was 88.06 +/- 147.42 mg, vasodilator ion concentration of locally used herbs was 90.15 +/- 136.94 mg. The difference between vasodilator concentrations of groups was more evident; 5.39 +/- 9.80 mg and 14.32 +/- 66.48 mg for locally and systemically used herbs respectively. CONCLUSIONS: This study showed that herbal remedies used for the treatment of hemorrhoid in Turkey contain vasoactive and especially vasoconstrictor ions. Vasoconstrictor agents could amplify each others' effects as it has been previously shown, therefore, it is probable that the vasoconstrictor ion contents could contribute to the curative effects of herbals in the treatment of hemorrhoids.

Clopidogrel resistance: a diagnostic challenge.

No clear and generally accepted definition of clopidogrel resistance has been achieved up to now. We believe that the new point-of-care assays of platelet function may help the clinicians to overcome to define clopidogrel resistance especially in patients undergoing percutaneous coronary intervention in whom the level of inhibition of platelets is clinically essential.

Protective efficiacy of taurine against pulmonary edema progression: experimental study.

Re-expansion pulmonary edema (RPE) is an acute, rare and potentially lethal complication. Its beginning is sudden and dramatic. The mechanism is not yet fully understood. Some authors suggest that it may occur after rapid re-inflation of a collapsed lung. It was reported by other authors that it may relate to surfactant depletion or may result from hypoxic capillary damage, leading to increased capillary permeability. In RPE, unilateral lung injury is initiated by cytotoxic oxygen metabolites and temporally associated with an influx of polymorphonuclear neutrophils. These toxic oxygen products are the results of re-oxygenation of a collapsed lung. Treatment of re-expansion pulmonary edema is basically preventive.

The concentration-dependent contractile effect of methylene blue in the human internal mammary artery: a quantitative approach to its use in the vasoplegic syndrome.

OBJECTIVE: To quantitate the contractile effect of methylene blue on isolated human internal mammary artery (IMA) as used in the vasoplegic syndrome. DESIGN: An in vitro experimental study. SETTING: Cardiovascular Pharmacology Laboratory, Department of Medical Pharmacology. PARTICIPANTS: IMA segments were used from 24 patients undergoing coronary artery bypass surgery. INTERVENTIONS: The responses to methylene blue, norepinephrine, and acetylcholine were recorded isometrically by a force-displacement transducer in an isolated organ bath. MEASUREMENT AND MAIN RESULTS: Methylene blue (10 nmol/L-100 micromol/L) produced concentration-dependent contraction in the arteries. The maximal contraction to methylene blue was 44.2% +/- 3.8% of KCl (68 mmol/L) maximum contraction; the pEC(50) (-log(10) of 50% effective concentration) value was 5.5 +/- 0.1. Methylene blue caused an insignificant leftward shift of the concentration-response curve of norepinephrine. Acetylcholine-induced relaxation in submaximal contracted rings with phenylephrine recovered nearly 6 hours after the methylene blue challenge. CONCLUSION: Methylene blue caused concentration-dependent contraction in human IMAs. Furthermore, the inhibition of ACh-induced relaxation for 6 hours after the methylene blue challenge points out an additional mechanism (ie, receptor occupation). The concentration-dependent contractile effect of methylene blue justifies its use in the vasoplegic syndrome. The findings also suggest that the time course of contraction is longer than the exposure to methylene blue.

Serum aluminium levels in glue-sniffer adolescent and in glue containers.

Glue sniffing is a serious medical problem among teenagers. Various chemical substances such as toluene and benzene containing glues have been reported to be toxic. It has been demonstrated that some toxic metals such as lead are elevated in the blood of solvent-addicted patients. Whereas aluminium is an element that has toxic effects on neurological, hematopoetic system and bone metabolism. We want to determine the serum levels of aluminium in glue-sniffer adolescents in comparison with healthy subjects. In addition, we compared aluminium levels of different commercial glue preparations (i.e. metal and plastic containers), to determine which type of container is better for less aluminium toxicity. We measured serum levels of aluminium in 37 glue-sniffer and 37 healthy subjects using atomic absorption spectrophotometry. The average duration of glue-sniffer was 3.8 +/- 0.8 years. We also measured aluminium levels of 10 commercial glue preparations that seven of them with metal and three with plastic containers. We found that serum levels of aluminium were 63.29 +/- 13.20 ng/ml and 36.7 +/- 8.60 ng/ml in glue-sniffer and in control subjects, respectively (P < 0.001). The average aluminium level in the glues was 8.6 +/- 3.24 ng/g in the preparations with metal containers, whereas 3.03 +/- 0.76 ng/g with plastic containers (P < 0.001). Therefore, to decrease the incidence of aluminium toxicity in glue-sniffers, it may be a good step to market of glue preparations in plastic instead of metal containers.

Dexmedetomidine produces dual alpha2-adrenergic agonist and alpha1-adrenergic antagonist actions on human isolated internal mammary artery.

OBJECTIVE: To investigate the direct effects of dexmedetomidine (DEX) on isolated human internal mammary artery (IMA). DESIGN: In vitro experimental study. SETTING: Cardiovascular Pharmacology Laboratory, Department of Pharmacology, Gulhane School of Medicine, Ankara, Turkey. PARTICIPANTS: IMA segments were obtained from 18 patients undergoing coronary artery bypass surgery. INTERVENTIONS: The response in IMA was recorded isometrically by a force displacement transducer in isolated organ baths. DEX-induced contractions were tested in the presence of the alpha2-adrenoceptor antagonist yohimbine (10(-7) mol/L) and the alpha1-adrenoceptor antagonist prazosin (10(-8) M). The effect of DEX (10(-7), 10(-6), and 10(-5) mol/L) on phenylephrine (10(-9)-3 x 10(-4) mol/L)-induced contactions was also tested. MEASUREMENT AND MAIN RESULTS: DEX (10(-9) mol/L-3 x 10(-5) mol/L) caused contraction in IMA segments. The contraction at lower concentrations of DEX (10(-9) mol/L-3 x 10(-7) mol/L) was attenuated by yohimbine (10(-7) mol/L), whereas prazosin (10(-8) mol/L) attenuated the contractions at higher concentrations of DEX (10(-6) mol/L-3 x 10(-5) mol/L). Incubation of IMA segments with high concentrations of DEX (10(-6) mol/L and 10(-5) mol/L) caused an inhibition of phenylephrine (10(-9) mol/L-3 x 10(-4) mol/L)-induced contraction. CONCLUSION: These data suggest that DEX causes contraction by activating alpha2-adrenoceptors at lower concentrations, but it may also activate alpha1-adrenoceptors at higher concentrations in IMA. The action of DEX on phenylephrine-induced contraction may be related to an alpha1-adrenoceptor antagonistic effect produced via partial alpha1-adrenoceptor agonistic action.

The local antinociceptive actions of nonsteroidal antiinflammatory drugs in the mouse radiant heat tail-flick test.

BACKGROUND: While many preclinical models detect the analgesic activity of nonsteroidal antiinflammatory drugs (NSAIDs), the radiant heat tail-flick response has repeatedly been insensitive to this class of drugs. As the tail-flick test involves nociceptive processing at spinal circuits with supraspinal modulation, it seems reasonable to assume that the NSAIDs should not modify strong nociceptive stimuli, since the primary site of action of NSAIDs is likely to be in the periphery. METHODS: We injected 3-300 mug of diclofenac, dipyrone, ketorolac, lysine acetyl salicylate, and sodium salicylate intradermally into mice tails and evaluated the tail-flick response to radiant heat. These results were compared with intraperitoneally injected controls. We also evaluated the ability of naloxone to reverse the observed effects. RESULTS: Intradermal injection of each NSAID produced a dose-dependent increase in tail-flick latency. Intraperitoneal NSAIDs injection produced no antinociceptive effects. Naloxone pretreatment had no effect on the antinociceptive effects of intradermal diclofenac, ketorolac, lysine acetyl salicylate, and sodium salicylate. Naloxone completely blocked the antinociceptive effects of intradermal dipyrone. CONCLUSIONS: Local, but not systemic, administration of NSAIDs produced antinociception in the tail-flick thermal assay. The endogenous opioid system contributes to the peripheral antinociceptive effects of dipyrone, but not to that of diclofenac, ketorolac, lysine acetyl salicylate, or sodium salicylate, suggesting differences in the mechanisms of action among the NSAIDs.

Lipophilic components of different therapeutic mud species.

OBJECTIVE: Mud, which contains organic and mineral ingredients, is used for the treatment of several degenerative diseases. It has been proposed that beneficial effects of mud are not only related to its local thermal effects, but also to its chemical components. Unlike hydrophilic components, the lipophilic components of the mud extract have not been described precisely thus far. Thus, we aimed to determine the lipophilic components of the different mud species. METHODS: Three different mud species (e.g., krenogen, tone, and fango) were analyzed by using gas chromatography-mass spectrometry (GC-MS). RESULTS: There were organic substances with fatty-acid structures found in the structure of mud. Torf mud species contain the most compounds. The compounds of three mud species differ from each other. CONCLUSIONS: The chemical structure of mud does not only contain hydrophilic organic substances, such as humic, fulmic, and ulmic acids, but also low-molecular-weighted organic substances composed of fatty acids in the majority. Moreover, it would not be appropriate to explain mud with a single term, since it has different chemical structures and a new classification of the mud species is required.

Testosterone relaxes human internal mammary artery in vitro.

Preliminary clinical studies of testosterone therapy in male patients with coronary artery disease raised promising results. However, there is no study on in vitro effects of testosterone in human isolated arteries. We investigated the effect of testosterone on contractile tone of human isolated internal mammary artery. The responses in human internal mammary artery (IMA) were recorded isometrically by a force-displacement transducer in isolated organ baths. Testosterone (10 nM to 100 microM) was added cumulatively to organ baths either at rest or after precontraction with KCl (68 mM) and PGF2alpha (10 microM). Testosterone-induced relaxations were tested in the presence of cyclooxygenase inhibitor indomethacin (10 microM), nitric oxide synthase inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME, 1 microM), nonselective large-conductance Ca2+-activated and voltage-sensitive K+ channel inhibitor tetraethylammonium (TEA, 1 mM), ATP-sensitive K+ channel inhibitor glibenclamide (GLI, 100 microM), and voltage-sensitive K+ channel inhibitor 4-aminopyridine (4-AP, 1 mM). Testosterone produced relaxation in human IMA (Emax 33% and 41% of KCl- and PGF2alpha-induced contraction, respectively). Vehicle had no significant relaxant effect. Except for TEA, the relaxation at low concentrations is not affected by either K+ channel inhibitors (GLI and 4-AP) or L-NAME and indomethacin. We report for the first time that supraphysiological concentrations of testosterone induce relaxation in IMA. This response may occur in part via large-conductance Ca2+-activated K+ channel-opening action.

The relationship between risk factors and testosterone-induced relaxations in human internal mammary artery.

In human internal mammary artery (IMA), testosterone induces vasodilation that shows marked variability among patients. We aimed to investigate the relationship of this variability with cardiovascular risk factors. Cumulative relaxations to testosterone after precontraction with KCl were examined in IMA segments from patients with identified cardiovascular risk factors such as hypercholesterolemia, diabetes, hypertension, smoking, age, gender, body mass index (BMI), and number of occluded vessels. Testosterone responses were significantly diminished in subjects with 3 compared with 1 risk factor. Hypercholesterolemia independently influenced testosterone responses by significantly decreasing its maximum, and smoking significantly decreased the sensitivity to testosterone. Thus, the variability observed in testosterone-induced vascular relaxations may in part be related to differences in risk factors present among the individuals studied.