Testosterone-dependent increase in blood pressure is mediated by elevated Cyp4A expression in fructose-fed rats. Mol Cell Biochem. 2012;359:409-418. [PMID: 21894443 DOI: 10.1007/s11010-011-1035-7]

20-Hydroxyeicosatetraenoic acid (20-HETE): Bioactions, receptors, vascular function, cardiometabolic disease and beyond

Vascular function is dynamically regulated and dependent on a bevy of cell types and factors that work in concert across the vasculature. The vasoactive eicosanoid, 20-Hydroxyeicosatetraenoic acid (20-HETE) is a key player in this system influencing the sensitivity of the vasculature to constrictor stimuli, regulating endothelial function, and influencing the renin angiotensin system (RAS), as well as being a driver of vascular remodeling independent of blood pressure elevations. Several of these bioactions are accomplished through the ligand-receptor pairing between 20-HETE and its high-affinity receptor, GPR75. This 20-HETE axis is at the root of various vascular pathologies and processes including ischemia induced angiogenesis, arteriogenesis, septic shock, hypertension, atherosclerosis, myocardial infarction and cardiometabolic diseases including diabetes and insulin resistance. Pharmacologically, several preclinical tools have been developed to disrupt the 20-HETE axis including 20-HETE synthesis inhibitors (DDMS and HET0016), synthetic 20-HETE agonist analogues (20-5,14-HEDE and 20-5,14-HEDGE) and 20-HETE receptor blockers (AAA and 20-SOLA). Systemic or cell-specific therapeutic targeting of the 20-HETE-GPR75 axis continues to be an invaluable approach as studies examine the molecular underpinnings activated by 20-HETE under various physiological settings. In particular, the development and characterization of 20-HETE receptor blockers look to be a promising new class of compounds that can provide a considerable benefit to patients suffering from these cardiovascular pathologies.

The association between growth patterns and blood pressure in children and adolescents: A cross-sectional study of seven provinces in China

Aimed to investigate the associations between different growth patterns with high blood pressure, and further examine the mediation effect of BMI between growth patterns and high blood pressure among children and adolescents. A total of 31581 children and adolescents aged 7–18 years were selected based on the stratified cluster sampling method. Logistics regression models were used to calculate the odds rations (ORs) and 95% confidence interval (95%CI) of the association between different growth patterns and high blood pressure. Mediation effect analyses were applied to estimate the effect of BMI on the increase of blood pressure levels in different growth patterns. In different sex and ages, compared to reference group of normal growth, blood pressure levels and prevalence of high blood pressure of the catch‐up growth were higher, but that of the catch‐down growth were lower. The prevalence of high blood pressure was 11.69%, 16.06%, and 9.68% in normal growth, catch‐up growth, and catch‐down growth, respectively. In total, compared with the normal growth pattern, the ORs (95%CI) of high blood pressure, high systolic blood pressure and high diastolic blood pressure in the catch‐up growth were 1.171(1.073,1.280), 1.110(1.001,1.230) and 1.141(1.025,1.270) (p < .05), respectively. Additionally, the mediation effect of current BMI existed in the association between blood pressure levels and different growth patterns, particularly in boys. Our findings suggested that different growth patterns after birth could modify blood pressure, and the potential risks of high blood pressure could be increased by catch‐up growth at childhood and adolescence.

Sex differences in eicosanoid formation and metabolism: A possible mediator of sex discrepancies in cardiovascular diseases

Arachidonic acid is metabolized by cyclooxygenase, lipoxygenase, and cytochrome P450 enzymes to produce prostaglandins, leukotrienes, epoxyeicosatrienoic acids (EETs), and hydroxyeicosatetraenoic acids (HETEs), along with other eicosanoids. Eicosanoids have important physiological and pathological roles in the body, including the cardiovascular system. Evidence from several experimental and clinical studies indicates differences in eicosanoid levels, as well as in the activity or expression levels of their synthesizing and metabolizing enzymes between males and females. In addition, there is a clear state of gender specificity in cardiovascular diseases (CVD), which tend to be more common in men compared to women, and their risk increases significantly in postmenopausal women compared to younger women. This could be largely attributed to sex hormones, as androgens exert detrimental effects on the heart and blood vessels, whereas estrogen exhibits cardioprotective effects. Many of androgen and estrogen effects on the cardiovascular system are mediated by eicosanoids. For example, androgens increase the levels of cardiotoxic eicosanoids like 20-HETE, while estrogens increase the levels of cardioprotective EETs. Thus, sex differences in eicosanoid levels in the cardiovascular system could be an important underlying mechanism for the different effects of sex hormones and the differences in CVD between males and females. Understanding the role of eicosanoids in these differences can help improve the management of CVD.

Unraveling the Role of 12- and 20- HETE in Cardiac Pathophysiology: G-Protein-Coupled Receptors, Pharmacological Inhibitors, and Transgenic Approaches

ABSTRACT

Arachidonic acid-derived lipid mediators play crucial roles in the development and progression of cardiovascular diseases. Eicosanoid metabolites generated by lipoxygenases and cytochrome P450 enzymes produce several classes of molecules, including the epoxyeicosatrienoic acid (EET) and hydroxyeicosatetraenoic acids (HETE) family of bioactive lipids. In general, the cardioprotective effects of EETs have been documented across a number of cardiac diseases. In contrast, members of the HETE family have been shown to contribute to the pathogenesis of ischemic cardiac disease, maladaptive cardiac hypertrophy, and heart failure. The net effect of 12(S)- and 20-HETE depends upon the relative amounts generated, ratio of HETEs:EETs produced, timing of synthesis, as well as cellular and subcellular mechanisms activated by each respective metabolite. HETEs are synthesized by and affect multiple cell types within the myocardium. Moreover, cytochrome P450-derived and lipoxygenase- derived metabolites have been shown to directly influence cardiac myocyte growth and the regulation of cardiac fibroblasts. The mechanistic data uncovered thus far have employed the use of enzyme inhibitors, HETE antagonists, and the genetic manipulation of lipid-producing enzymes and their respective receptors, all of which influence a complex network of outcomes that complicate data interpretation. This review will summarize and integrate recent findings on the role of 12(S)-/20-HETE in cardiac diseases.

Ovariectomy, but not orchiectomy, exacerbates metabolic syndrome after maternal high-fructose intake in adult offspring

High fructose diet is associated with the global metabolic syndrome (MtS) pandemic. MtS develops in early life, depending on prenatal and postnatal nutritional status. We hypothesized that ovariectomy increases the chances of developing MtS in adult offspring following high fructose intake by the mother. Pregnant C57BL/6J mouse dams drank water with or without 20% fructose during pregnancy and lactation. After weaning, the pups were fed regular chow. The offspring were evaluated until they were 7 months of age after the mice in each group, both sexes, were gonadectomized at 4 weeks of age. The offspring (both sexes) of the dams who had high fructose intake developed MtS. In the offspring of dams who drank tap water, orchiectomy increased the body weight gain and body fat accumulation, while ovariectomy increased the body fat accumulation as compared to the sham controls. In the offspring of dams with high fructose intake, orchiectomy decreased the body weight gain, body fat accumulation, visceral adiposity, and glucose intolerance, while ovariectomy exacerbated all of them as compared to the sham operations. These data indicate that ovariectomy encourages the development of MtS in adult offspring after maternal high fructose intake, while orchiectomy prevents the development of MtS. The sex difference indicates that male and female sex hormones play contradictory roles in the development of MtS.

Maternal high-fructose intake during pregnancy and lactation induces metabolic syndrome in adult offspring

BACKGROUND/OBJECTIVES

Nutritional status and food intake during pregnancy and lactation can affect fetal programming. In the current metabolic syndrome epidemic, high-fructose diets have been strongly implicated. This study investigated the effect of maternal high-fructose intake during pregnancy and lactation on the development of metabolic syndrome in adult offspring.

SUBJECTS/METHODS

Drinking water with or without 20% fructose was administered to female C57BL/6J mice over the course of their pregnancy and lactation periods. After weaning, pups ate regular chow. Accu-Chek Performa was used to measure glucose levels, and a tail-cuff method was used to examine systolic blood pressure. Animals were sacrificed at 7 months, their livers were excised, and sections were stained with Oil Red O and hematoxylin and eosin (H&E) staining. Kidneys were collected for gene expression analysis using quantitative real-time Polymerase chain reaction.

RESULTS

Adult offspring exposed to maternal high-fructose intake during pregnancy and lactation presented with heavier body weights, fattier livers, and broader areas under the curve in glucose tolerance test values than control offspring. Serum levels of alanine aminotransferase, aspartate aminotransferase, glucose, triglycerides, and total cholesterol and systolic blood pressure in the maternal high-fructose group were higher than that in controls. However, there were no significant differences in mRNA expressions of renin-angiotensin-aldosterone system genes and sodium transporter genes.

CONCLUSIONS

These results suggest that maternal high-fructose intake during pregnancy and lactation induces metabolic syndrome with hyperglycemia, hypertension, and dyslipidemia in adult offspring.

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Te increase in the prevalence of arterial hypertension (AH) in populations, ineffective treatment, the need for risk stratifcation, prevention, early diagnosis and successful treatment, actualize genomic studies to develop a personalized therapeutic approach to AH. Te review investigates the possible genetically determined mechanisms of the development of hypertension and endothelial dysfunction caused by polymorphism of the genes of endothelial nitric oxide synthase (eNOS) and enzymes of phases I and II of the xenobiotics detoxifcation system. Te probable interaction of both systems under the influence of harmful environmental factors, including tobacco smoking, and in the gestational period is discussed. It is proposed to study AH candidate genes in the xenobiotics detoxifcation system, the carriage of different variants of which can determine the sensitivity or resistance to antihypertensive pharmacotherapy, which can be useful for developing of the personalized tactics of managing patients with AH.

Elevated 20-HETE in metabolic syndrome regulates arterial stiffness and systolic hypertension via MMP12 activation

Arterial stiffness plays a causal role in development of systolic hypertension. 20-hydroxyeicosatetraeonic acid (20-HETE), a cytochrome P450 (CYP450)-derived arachidonic acid metabolite, is known to be elevated in resistance arteries in hypertensive animal models and loosely associated with obesity in humans. However, the role of 20-HETE in the regulation of large artery remodeling in metabolic syndrome has not been investigated. We hypothesized that elevated 20-HETE in metabolic syndrome increases matrix metalloproteinase 12 (MMP12) activation leading to increased degradation of elastin, increased large artery stiffness and increased systolic blood pressure. 20-HETE production was increased ~7 fold in large, conduit arteries of metabolic syndrome (JCR:LA-cp, JCR) vs. normal Sprague-Dawley (SD) rats. This correlated with increased elastin degradation (~7 fold) and decreased arterial compliance (~75% JCR vs. SD). 20-HETE antagonists blocked elastin degradation in JCR rats concomitant with blocking MMP12 activation. 20-HETE antagonists normalized, and MMP12 inhibition (pharmacological and MMP12-shRNA-Lnv) significantly improved (~50% vs. untreated JCR) large artery compliance in JCR rats. 20-HETE antagonists also decreased systolic (182 ± 3 mmHg JCR, 145 ± 3 mmHg JCR + 20-HETE antagonists) but not diastolic blood pressure in JCR rats. Whereas diastolic pressure was fully angiotensin II (Ang II)-dependent, systolic pressure was only partially Ang II-dependent, and large artery stiffness was Ang II-independent. Thus, 20-HETE-dependent regulation of systolic blood pressure may be a unique feature of metabolic syndrome related to high 20-HETE production in large, conduit arteries, which results in increased large artery stiffness and systolic blood pressure. These findings may have implications for management of systolic hypertension in patients with metabolic syndrome.

1-Aminobenzotriazole: A Mechanism-Based Cytochrome P450 Inhibitor and Probe of Cytochrome P450 Biology

1-Aminobenzotriazole (1-ABT) is a pan-specific, mechanism-based inactivator of the xenobiotic metabolizing forms of cytochrome P450 in animals, plants, insects, and microorganisms. It has been widely used to investigate the biological roles of cytochrome P450 enzymes, their participation in the metabolism of both endobiotics and xenobiotics, and their contributions to the metabolism-dependent toxicity of drugs and chemicals. This review is a comprehensive evaluation of the chemistry, discovery, and use of 1-aminobenzotriazole in these contexts from its introduction in 1981 to the present.

Role of 20-Hydroxyeicosatetraenoic Acid (20-HETE) in Androgen-Mediated Cell Viability in Prostate Cancer Cells

20-Hydroxyeicosatetraenoic acid (20-HETE) is generated intracellularly through the ω-hydroxylation of arachidonic acid by the cytochrome P450 (in humans, CYP4A11 and CYP4F2). 20-HETE induces mitogenic responses in different cancer cells. The aim of this study was to analyze how 20-HETE impacts cell survival, proliferation, and apoptosis in prostate cancer cells. Incubation of the human androgen-sensitive cells (LNCaP) with 1-10 μM HET0016 (a selective inhibitor of 20-HETE synthesis) reduced cell viability by 49*-64%* (*p < 0.05 vs. control). This was explained by a reduction in cell proliferation (vehicle, 46 ± 3%; 1 μM, 23 ± 3%*; 10 μM, 28 ± 3%*) and by an increase in apoptosis (vehicle, 2.1 ± 0%; 1 μM, 16 ± 4%*; 10 μM, 31 ± 3%*). Furthermore, the increase in LNCaP cell viability induced by dihydrotestosterone (DHT, 0.1 nM) was abrogated by 30*-42%* by 1-10 μM HET0016. Incubation with 20-HETE (5-1000 nM) increased LNCaP cell viability up to 50%*, together with a 70%* reduction in apoptosis. PC-3 (androgen-insensitive) cell viability was not affected by either HET0016 or 20-HETE. In LNCaP cells, HET0016 (10 μM) diminished the expression of androgen receptors (AR): messenger RNA (mRNA) (40%*) and protein (50%*). DHT (10 nM) augmented CYP4F2 protein expression (1.9-fold*) and 20-HETE levels (50%*). Oppositely, enzalutamide (AR antagonist) reduced CYP4F2 mRNA and protein expressions by 30 and 25%, respectively. Thus, intracellular availability of 20-HETE is necessary to sustain LNCaP cell viability. 20-HETE may act as a signaling molecule in the pathways involved in LNCaP cell viability upon stimulation of the AR. This effect may be partially attributed to its role on securing normal AR expression levels that in turn contribute to maintain intracellular levels of 20-HETE.

Effects of testosterone on mean arterial pressure and aquaporin (AQP)-1, 2, 3, 4, 6 and 7 expressions in the kidney of orchidectomized, adult male Sprague-Dawley rats

We hypothesized that higher blood pressure in males than females could be due to testosterone effects on aquaporin (AQP) expression in kidneys.

METHODS

Orchidectomized adult male Sprague-Dawley (SD) rats received seven days subcutaneous testosterone treatment (125 μg/kg/day or 250 μg/kg/day), with or without flutamide or finasteride. Following completion of treatment, MAP was determined in rats under anaesthesia via carotid artery cannulation. In another cohort of rats, kidneys were removed following sacrifice and AQP-1, 2, 3, 4, 6 and 7 protein and mRNA levels were determined by Western blotting and Real-time PCR respectively. Distribution of AQP subunits' protein in the nephrons were visualized by immunofluorescence.

RESULTS

Testosterone caused MAP, AQP-1, 2, 4, 6 and 7 protein and mRNA levels in kidneys to increase while AQP-3 protein and mRNA levels in kidneys to decrease (p < 0.05). AQP-1 and 7 were found to be distributed in the proximal convoluted tubule (PCT) while AQP-2, 3, 4 and 6 were found to be distributed in the collecting ducts (CD). Effects of testosterone were antagonized by flutamide and finasteride.

CONCLUSIONS

Elevated expression of AQP-1, 2, 4, 6 and 7 under testosterone influence in kidneys could lead to increase H₂O reabsorption which eventually lead to increase in blood pressure.

Androgen-sensitive hypertension associated with soluble guanylate cyclase-α1 deficiency is mediated by 20-HETE

Dysregulated nitric oxide (NO) signaling contributes to the pathogenesis of hypertension, a prevalent and often sex-specific risk factor for cardiovascular disease. We previously reported that mice deficient in the α1-subunit of the NO receptor soluble guanylate cyclase (sGCα1 (-/-) mice) display sex- and strain-specific hypertension: male but not female sGCα1 (-/-) mice are hypertensive on an 129S6 (S6) but not a C57BL6/J (B6) background. We aimed to uncover the genetic and molecular basis of the observed sex- and strain-specific blood pressure phenotype. Via linkage analysis, we identified a suggestive quantitative trait locus associated with elevated blood pressure in male sGCα1 (-/-)S6 mice. This locus encompasses Cyp4a12a, encoding the predominant murine synthase of the vasoconstrictor 20-hydroxy-5,8,11,14-eicosatetraenoic acid (20-HETE). Renal expression of Cyp4a12a in mice was associated with genetic background, sex, and testosterone levels. In addition, 20-HETE levels were higher in renal preglomerular microvessels of male sGCα1 (-/-)S6 than of male sGCα1 (-/-)B6 mice. Furthermore, treating male sGCα1 (-/-)S6 mice with the 20-HETE antagonist 20-hydroxyeicosa-6(Z),15(Z)-dienoic acid (20-HEDE) lowered blood pressure. Finally, 20-HEDE rescued the genetic background- and testosterone-dependent impairment of acetylcholine-induced relaxation in renal interlobar arteries associated with sGCα1 deficiency. Elevated Cyp4a12a expression and 20-HETE levels render mice susceptible to hypertension and vascular dysfunction in a setting of sGCα1 deficiency. Our data identify Cyp4a12a as a candidate sex-specific blood pressure-modifying gene in the context of deficient NO-sGC signaling.

Association of testosterone with estrogen abolishes the beneficial effects of estrogen treatment by increasing ROS generation in aorta endothelial cells

Testosterone has been added to hormone replacement therapy to treat sexual dysfunction in postmenopausal women. Whereas estrogen has been associated with vascular protection, the vascular effects of testosterone are contradictory and the effects of its association with estrogen are largely unknown. In this study we determined the effects of testosterone associated with conjugated equine estrogen (CEE) on vascular function using a model of hypertensive postmenopausal female: ovariectomized spontaneously hypertensive rats. Female spontaneously hypertensive rats were divided into sham-operated, ovariectomized (OVX), and OVX treated for 15 days with either CEE alone (OVX+CEE) or associated with testosterone (OVX+CEE+T). Angiotensin II (ANG II)-induced contraction was markedly increased in aortic rings from OVX compared with sham-operated rats. CEE treatment restored ANG-II responses, a beneficial effect abrogated with CEE+T. CEE treatment also increased endothelium-dependent relaxation, which was impaired in OVX rats. This effect was lost by CEE+T. Treatment of aortas with losartan (ANG-II type-1 receptor antagonist) or apocynin (NADPH-oxidase inhibitor) restored the endothelium-dependent relaxation in OVX and CEE+T, establishing an interplay between ANG-II and endothelial dysfunction in OVX and CEE+T. The benefits by CEE were associated with downregulation of NADPH-oxidase subunits mRNA expression and decreased reactive oxygen species generation. The association of testosterone with CEE impairs the benefits of estrogen on OVX-associated endothelial dysfunction and reactive oxygen species generation in rat aorta by a mechanism that involves phosphorylation of the cytosolic NADPH-oxidase subunit p47 phox.

Androgen-induced hypertension in angiotensinogen deficient mice: role of 20-HETE and EETS

20-HETE is a potent inducer of endothelial ACE in vitro and administration of lisinopril or losartan attenuates blood pressure in models of 20-HETE-dependent hypertension. The present study was undertaken to further define the relationship between 20-HETE and the renin-angiotensin system in hypertension using an angiotensinogen-deficient mouse (Agt+/-). Treatment of male AGT+/- with 5α-dihydrotestosterone (DHT) increased systolic BP from 102±2 to 125±3mmHg; in comparison, the same treatment raised BP in wild type (WT) from 110±2 to 138±2mmHg. DHT increased vascular 20-HETE levels in AGT+/- and WT from 1.5±0.7 and 2.1±0.6 to 13.0±2.0 and 15.8±4.0ng/mg, respectively. Concurrent treatment with the 20-HETE antagonist, 20-hydroxyeicosa-6(Z),15(Z)-dienoic acid (20-HEDE) prevented the increases in BP in both AGT+/- and WT mice. Administration of 20-HEDE at the peak of the DHT-induced BP increase (12 days) reduced BP to basal levels after 48h. Interestingly, basal levels of renal microvascular EETs were higher in AGT+/- compared to WT (55.2±9.7 vs 20.0±4.1ng/mg) and treatment of AGT+/- with DHT decreased the levels of EETs (28.4±5.1ng/mg). DHT-mediated changes in vascular EET level were not observed in WT mice. Vascular Cyp4a12 and ACE protein levels were increased in both AGT+/- and WT by 30-40% and decreased with concomitant administration of 20-HEDE. Lisinopril was as effective as 20-HEDE in preventing DHT-mediated increases in BP in both AGT+/- and WT mice. This study substantiates our previous findings that the RAS plays an important role in 20-HETE-mediated hypertension. It also proposes a novel interaction between 20-HETE and EETs.

Determination of major UDP-glucuronosyltransferase enzymes and their genotypes responsible for 20-HETE glucuronidation

The compound 20-HETE is involved in numerous physiological functions, including blood pressure and platelet aggregation. Glucuronidation of 20-HETE by UDP-glucuronosyltransferases (UGTs) is thought to be a primary pathway of 20-HETE elimination in humans. The present study identified major UGT enzymes responsible for 20-HETE glucuronidation and investigated their genetic influence on the glucuronidation reaction using human livers (n = 44). Twelve recombinant UGTs were screened to identify major contributors to 20-HETE glucuronidation. Based on these results, UGT2B7, UGT1A9, and UGT1A3 exhibited as major contributors to 20-HETE glucuronidation. The Km values of 20-HETE glucuronidation by UGT1A3, UGT1A9, and UGT2B7 were 78.4, 22.2, and 14.8 μM, respectively, while Vmax values were 1.33, 1.78, and 1.62 nmol/min/mg protein, respectively. Protein expression levels and genetic variants of UGT1A3, UGT1A9, and UGT2B7 were analyzed in human livers using Western blotting and genotyping, respectively. Glucuronidation of 20-HETE was significantly correlated with the protein levels of UGT2B7 (r(2) = 0.33, P < 0.001) and UGT1A9 (r(2) = 0.31, P < 0.001), but not UGT1A3 (r(2) = 0.02, P > 0.05). A correlation between genotype and 20-HETE glucuronidation revealed that UGT2B7 802C>T, UGT1A9 -118T9>T10, and UGT1A9 1399T>C significantly altered 20-HETE glucuronide formation (P < 0.05-0.001). Increased levels of 20-HETE comprise a risk factor for cardiovascular diseases, and the present data may increase our understanding of 20-HETE metabolism and cardiovascular complications.

Way back for fructose and liver metabolism: Bench side to molecular insights

The World Health Organization recommends that the daily intake of added sugars should make up no more than 10% of total energy. The consumption of sugar-sweetened beverages is the main source of added sugars. Fructose, together with glucose, as a component of high fructose corn syrups or as a component of the sucrose molecule, is one of the main sweeteners present in this kind of beverages. Data from prospective and intervention studies clearly point to high fructose consumption, mainly in the form of sweetened beverages, as a risk factor for several metabolic diseases in humans. The incidence of hypertension, nonalcoholic fatty liver disease (NAFLD), dyslipidemia (mainly hypertriglyceridemia), insulin resistance, type 2 diabetes mellitus, obesity, and the cluster of many of these pathologies in the form of metabolic syndrome is higher in human population segments that show high intake of fructose. Adolescent and young adults from low-income families are especially at risk. We recently reviewed evidence from experimental animals and human data that confirms the deleterious effect of fructose on lipid and glucose metabolism. In this present review we update the information generated in the past 2 years about high consumption of fructose-enriched beverages and the occurrence of metabolic disturbances, especially NAFLD, type 2 diabetes mellitus, and metabolic syndrome. We have explored recent data from observational and experimental human studies, as well as experimental data from animal and cell models. Finally, using information generated in our laboratory and others, we provide a view of the molecular mechanisms that may be specifically involved in the development of liver lipid and glucose metabolic alterations after fructose consumption in liquid form.

The vasodilatory effect of testosterone on renal afferent arterioles

BACKGROUND

Sex differences exist in a variety of cardiovascular and renal diseases, and testosterone may contribute to the discrepancy. Afferent arterioles (Af-Arts) are the major resistance vessels in the kidney, and they play an important role in the development of renal injury and hypertension.

OBJECTIVE

We sought to determine the acute effect and underlying mechanism(s) of action of testosterone on Af-Arts.

METHODS

The mRNA expression of androgen receptors (ARs) in microdissected Af-Arts was measured by reverse transcription-polymerase chain reaction (RT-PCR). An in vitro microperfusion model was used to measure the diameter of Af-Arts in mice. Nitric oxide (NO) was evaluated by an NO-sensitive fluorescent dye, 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate.

RESULTS

Testosterone had no effect on microperfused Af-Arts when added to the bath. Therefore, we preconstricted the Af-Arts to approximately 30% with norepinephrine (10(-6) M); administration of testosterone (10(-9)-10(-7) M) subsequently dilated the Af-Arts in a dose-dependent manner (P < 0.001; n = 7). The AR mRNA was expressed in microdissected Af-Arts measured by RT-PCR. An AR antagonist, flutamide (10(-5) M), totally blocked the testosterone (10(-8) M)-induced vasodilator effect. Mean (SEM) NO production of the Af-Art wall was increased when testosterone was added to the bath solution after norepinephrine treatment, from 278.4 (12.1) U/min to 351.2 (33.1) U/min (P < 0.05; n = 3). In the presence of NO inhibition with N(G)-nitro-L-arginine methyl ester (3 × 10(-4) M), the testosterone-induced dilatation was blunted compared with norepinephrine (P < 0.05).

CONCLUSIONS

Testosterone dilated preconstricted mouse Af-Arts in a dose-dependent manner by activation of ARs and partially mediated by NO.