SEARCH · Search PubMed

Results for “subtype”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,135 records · Page 63Linked to original sources

PubMed1992

Muscarinic receptor subtypes in bovine adrenal medulla.

Catecholamine secretion in the bovine adrenal medulla is evoked largely by nicotinic receptor activation. However, bovine adrenal medulla also contain muscarinic receptors that mediate several cell responses. To understand the physiological role of muscarinic receptors in the bovine adrenal medulla it is important to identify the pharmacological subtypes present in this tissue. For this, we analyzed the abilities of different selective muscarinic antagonists in displacing the binding of the non-selective antagonist [3H] quinuclidinyl benzylate to an enriched plasma membrane fraction prepared from bovine adrenal medulla. All the selective antagonists bind at least two bindings sites with different affinities. The binding profile of the sites with high proportion is similar to the M2 subtype and those present in low proportion have a M1 profile. However, some variation in the proportion of the sites for the different ligands suggest the presence of the third pharmacological subtype (M3). We conclude that the sites in high proportion (60-80%) correspond to M2 muscarinic subtypes, and the rest is constituted by M1 plus M3 subtypes. The presence of multiplicity of subtypes in the adrenal medulla membranes suggests a diversity of functions of muscarinic receptors in the adrenal gland.

Adrenal Medulla↗

PubMed1988

Mast cell subtypes from human lung tissue: their identification, separation, and functional characteristics.

The contribution of mast cell subtypes and their different mediators to the pathogenesis of chronic obstructive lung diseases (COLD) has not yet been established. In the present study, enzymatic digestion, centrifugal elutriation and Percoll gradient centrifugation were used to obtain two populations of mast cell subtypes from human lung tissue. Mast cell subtypes were challenged with anti-human IgE, propranolol, compound 48/80, or opsonized zymosan. Both subtypes were able to release histamine, but differed in the amount of the amine release. Only the formalin-sensitive and alcian blue-positive type (FS-AB) released histamine on challenge with opsonized zymosan. The same subtype was able to release leukotriene C4 (LTC4) after challenge with anti-human IgE. The other subtype, the formalin-insensitive and alcian blue-positive type (FI-AB), did not respond to opsonized zymosan and did not release LTC4 after challenge with anti-human IgE. Stimulation with propranolol or compound 48/80 did not release histamine from the FS-AB mast cells while the FI-AB mast cells released only about 10% of their histamine content upon challenge with these secretagogues.

Histamine Release↗

PubMed1994

An examination of the validity of social subtypes in autism.

The validity of a social subtyping scheme forwarded by Wing and her colleagues is examined in a sample of 53 autistic individuals. Clinical ratings of subtype (aloof, passive, active-but-odd), IQ estimates, and measures of adaptive functioning and level of autism were obtained. Subjects were individually administered the Autism Diagnostic Observation Schedule (ADOS) by the principle examiner, who was blind to subtype assignment. The general findings supported the validity of aloof and active-but-odd subtypes as predictors of behavior across language/communication, reciprocal social interaction, and stereotyped behavior/restricted interest domains and suggested that individuals assigned to these respective groups differed in a number of important ways (e.g., level of autism, IQ, adaptive behavior). Partial support for an intermediate, passive subtype was garnered. The clinical utility of social subtypes is discussed as an important implication of this work.

Adolescent↗

PubMed1995

Ontogenic expression of two alpha-1 adrenergic receptor subtypes in the rat brain.

alpha-1A/D and alpha-1B adrenergic receptor subtype mRNA expression was studied during pre- and postnatal rat brain development. Oligonucleotide probes were generated to distinguish these two homologous subtypes by in situ histochemical analysis in E14, E16, E19, P0, P8, P14, P21, and adult animals. alpha-1B adrenergic receptor mRNA expression was noted as early as the E14 animal and demonstrated specific regional and temporal expression. alpha-1A/D adrenergic receptor mRNA expression was limited in the E19 and P0 animal but increased in intensity with aging. Specific regional and temporal expression differed between the two subtypes. The regional localization for both subtypes appeared to be stable after P21 but the intensity of expression for both subtypes decreased between P21 and adulthood, which is a finding that correlates with previous ligand-binding data. Different subtypes of homologous receptors have very different ontogenic patterns of distribution and may account for previous discrepancies in ligand-binding data and differential tissue responses to various ligands during development.

Animals↗

PubMed2001

Subtyping women with bulimia nervosa along dietary and negative affect dimensions: a replication in a treatment-seeking sample.

Recent cluster-analysis studies of women with bulimia nervosa (BN) have suggested two subtypes, a pure dietary subtype and a mixed dietary-negative affect. We aimed to replicate the subtyping findings in a clinical study group of 48 adult women with BN. Cluster analyses revealed a dietary-negative affect subtype (56% of cases) and a pure dietary subtype (44% of cases). The dietary-negative affect subtype was characterized by significantly greater eating-related attitudinal psychopathology and associated psychological disturbance. Our findings suggest that severe restraint is a central feature of BN and that affective disturbance, which occurs in roughly half of cases, is associated with greater eating-related attitudinal psychopathology and psychological symptomatology.

Adult↗

PubMed1997

Identification of alpha 1-adrenoceptor subtypes in the human prostatic urethra.

To identify the alpha 1-adrenoceptor subtypes in the human prostatic urethra, we compared the potencies of various alpha 1-adrenoceptor agonists and antagonists in inhibiting [3H]tamsulosin binding to human prostatic urethral membranes with their potencies in inhibiting the binding of (+)-beta-([125I]iodo-4-hydroxyphenyl)ethylaminomethyl-tetralone ([125I]HEAT) to cloned human alpha 1a, alpha 1b and alpha 1d subtypes. The alpha 1A-selective antagonists 5-methylurapidil and (+)niguldipine showed higher affinities for both cloned alpha 1a and urethral alpha 1-adrenoceptors than for cloned alpha 1b- and alpha 1d-adrenoceptors. NS-49, (R)-3'-(2-amino-1-hydroxyethyl)-4'-fluoromethanesulfonanilide hydrochloride, recently characterized as an alpha 1A-selective agonist, also showed high affinity for the cloned alpha 1a subtype and urethral alpha 1-adrenoceptors. Prazosin showed lower affinity for alpha 1-adrenoceptors in the human prostatic urethra than for any of the three cloned alpha 1-adrenoceptors. Comparison of the affinities of alpha 1-adrenoceptor agonists and antagonists for human prostatic urethral alpha 1-adrenoceptors to their affinities for the three cloned alpha 1 subtypes indicated a close correlation between the affinities for human urethral alpha 1 and the cloned alpha 1a-adrenoceptors. However, prazosin did not conform to this pattern. These findings suggest that the predominant alpha 1-adrenoceptor in the human urethra is the alpha 1A subtype, and that an alpha 1L subtype which has been characterised by its low affinity for prazosin, may also be present.

Adrenergic alpha-Agonists↗

PubMed1998

Comparative pharmacology of human adenosine receptor subtypes - characterization of stably transfected receptors in CHO cells.

Four adenosine receptor subtypes of the family of G protein-coupled receptors, designated A1, A2A, A2B and A3 are currently known. In this study all human subtypes were stably transfected into Chinese hamster ovary (CHO) cells in order to be able to study their pharmacological profile in an identical cellular background utilizing radioligand binding studies (A1, A2A, A3) or adenylyl cyclase activity assays (A2B). The A1 subtype showed the typical pharmacological profile with 2-chloro-N6-cyclopentyladenosine (CCPA) as the agonist with the highest affinity and a marked stereoselectivity for the N6-phenylisopropyladenosine (PIA) diastereomers. In competition with antagonist radioligand biphasic curves were observed for agonists. In the presence of GTP all receptors were converted to a single low affinity state indicating functional coupling to endogenous G proteins. For A2A adenosine receptors CGS 21680 (2-[p-(2-carboxyethyl)phenylethylamino]-5'-N-ethylcarboxamidoadeno sine) and N-ethylcarboxamidoadenosine (NECA) were found to be the most potent agonists followed by R- and S-PIA with minor stereoselectivity. The relative potencies of agonists for the A2B adenosine receptor could only be tested by measurement of receptor-stimulated adenylyl cyclase activity. NECA was the most potent agonist with an EC50-value of 2.3 microM whereas all other compounds tested were active at concentrations in the high micromolar range. Inhibition of NECA-stimulated adenylyl cyclase identified xanthine amino congener (XAC; 8-[4-[[[[(2-aminoethyl)amino]-carbonyl]methyl]oxy]phenyl]-1,3-dipropylxa nthine) as the most potent antagonist at this receptor subtype. The A3 receptor was characterized utilizing the nonselective agonist [3H]NECA. The N6-benzyl substituted derivatives of adenosine-5'-N-methyluronamide (MECA) turned out to be the most potent agonists. The notion of xanthine-insensitivity of the A3 receptor should be dropped at least for the human receptor as xanthines with submicromolar affinity were found. Overall, the pharmacological characteristics of the human receptors are similar to other species with some species-specific characteristics. In this study we present for the first time the comparative pharmacology of all known human adenosine receptor subtypes. The CHO cells with stably transfected adenosine receptors provide an identical cellular background for such a pharmacological characterization. These cells are valuable systems for further characterization of specific receptor subtypes and for the development of new ligands.

Adenosine↗

PubMed2001

Pharmacological analysis of wild-type alpha, gamma and delta subtypes of the human peroxisome proliferator-activated receptor.

Three distinct peroxisome proliferator-activated receptor (PPAR) cDNAs were isolated from human brain RNA. Whereas the PPARdelta subtype perfectly matched the amino acid sequences reported in the Genbank database, several differences were found for the PPARalpha (Lys(123)Met, Ala(268)Val, Gly(296)Ala and Val(444)Ala) and PPARgamma2 (Met(8)Ile, Pro(9)Ala, Met(186)Ile, Pro(187)Ala and the deletion of a Gln(213) residue) subtypes. A pharmacological analysis was undertaken by co-expressing each PPAR subtype with a reporter plasmid containing a luciferase gene under the transcriptional control of a synthetic, triplicated PPAR response element in either HepG2 or Cos-7 cells. Whereas fenofibrate unselectively activated the PPARalpha and PPARdelta subtypes, the related BM-17.0744 compound was more potent and selective for PPARalpha. The thiazolidine dione derivatives rosiglitazone and pioglitazone were potent and selective PPARgamma2 agonists. L-165041, reported as a selective and potent PPARdelta ligand, displayed in this specified transactivation system, apart from its highly efficacious PPARdelta agonist activity, partial and full agonism at, respectively, PPARalpha and PPARgamma2 subtypes. In conclusion, transcriptional control of a luciferase gene by wild-type PPAR subtypes provides powerful recombinant assays to evaluate ligand's efficacy at these nuclear receptors.

Amino Acid Sequence↗

PubMed2001

Apamin interacts with all subtypes of cloned small-conductance Ca2+-activated K+ channels.

The purpose of the present study was to examine how apamin interacts with the three cloned subtypes of small-conductance Ca2+-activated K+ channels (hSK1, rSK2 and rSK3). Expression of the SK channel subtypes in Xenopus laevis oocytes resulted in large outward currents (0.5-5 microA) after direct injection of Ca2+. In all three cases the Ca2+-activated K+ currents could be totally inhibited by 500 nM apamin. Dose-response curves revealed a subtype-specific affinity for the apamin-induced inhibition with IC50 values of 704 pM and 196 nM (biphasic) for hSK1, 27 pM for rSK2 and 4 nM for rSK3. Consistent with these results, membranes prepared from oocytes expressing the SK channel subtypes bound 125I-labelled apamin with distinct dissociation constants (Kd values) of approx. 390 pM for hSK1, 4 pM for rSK2 and 11 pM for rSK3. These results show that apamin binds to and blocks all three subtypes of cloned SK channels, and the distinct values for IC50 and Kd suggest that apamin may be useful for determining the expression pattern of SK channel subtypes in native tissue.

Animals↗

PubMed2002

Ischemic stroke subtypes: risk factors, functional outcome and recurrence.

The etiology of ischemic stroke affects its prognosis, outcome and management. Our aims were to determine risk factors, clinical and imaging variables and prognostic differences in acute ischemic stroke subtypes. In this study, we prospectively investigated 264 consecutive patients with acute ischemic stroke between 1996 and 2000. All of the patients were categorized to one of four major ischemic stroke subtype based on TOAST (Trial of Org 10172 in Acute Stroke Treatment) criteria. The mean age was greater in patients with stroke of undetermined etiology (SUE). Prevalence of hypertension was higher in patients with lacunar infarct (LAC) than other subtypes. Smoking was less frequent in patients with cardioembolism (CARD). The mean infarct size was largest in patients with large artery atherosclerosis (LAA) while there were no differences in location or conversion of the infarct into hemorrhage. The proportion of the patients with milder neurological deficits at entry was higher in patients with LAC subtype. The rate of independent patients were different between subtypes: 62% in LAC, 43% in CARD, 38% in SUE, 35% in LAA at discharge ( p=0.01), and 91% in LAC, 69% in CARD, 59% in SUE, 60% in LAA at 6 months ( p<0.001). Recurrence rates were not different between groups. We conclude that risk factors, clinical imaging variables are different among ischemic stroke subtypes and that neurological status on admission and during follow-up strongly favors LAC.

Adult↗

PubMed2005

Identification of cell-of-origin breast tumor subtypes in inflammatory breast cancer by gene expression profiling.

Inflammatory breast cancer (IBC) is an aggressive form of locally advanced breast cancer with high metastatic potential. Most patients have lymph node involvement at the time of diagnosis and 1/3 of the patients have distant metastases. In a previous study, we demonstrated that IBC is a distinct form of breast cancer in comparison with non-IBC. The aim of this study was to investigate the presence of the different molecular subtypes in our data set of 16 IBC and 18 non-IBC specimen. Therefore, we selected an 'intrinsic gene set' of 144 genes, present on our cDNA chips and common to the 'intrinsic gene set' described by Sorlie et al. [PNAS, 2003]. This set of genes was tested for performance in the Norway/Stanford data set by unsupervised hierarchical clustering. Expression centroids were then calculated for the core members of each of the five subclasses in the Norway/Stanford data set and used to classify our own specimens by calculating Spearman correlations between each sample and each centroid. We identified the same cell-of-origin subtypes in IBC as those already described in non-IBC. The classification was in good agreement with immunohistochemical data for estrogen receptor protein expression and cytokeratin 5/6 protein expression. Confirmation was done by an alternative unsupervised hierarchical clustering method. The robustness of this classification was assessed by an unsupervised hierarchical clustering with an alternative gene set of 141 genes related to the cell-of-origin subtypes, selected using a discriminating score and iterative random permutation testing. The contribution of the different cell-of-origin subtypes to the IBC phenotype was investigated by principal component analysis. Generally, the combined ErbB2-overexpressing and basal-like cluster was more expressed in IBC compared to non-IBC, whereas the combined luminal A, luminal B and normal-like cluster was more pronounced in non-IBC compared to IBC. The presence of the same molecular cell-of-origin subtypes in IBC as in non-IBC does not exclude the specific molecular nature of IBC, since gene lists that characterize IBC and non-IBC are entirely different from gene lists that define the different cell-of-origin subtypes, as evidenced by principal component analysis.

Adenocarcinoma↗

PubMed2005

Performance and private speech of children with attention-deficit/hyperactivity disorder while taking the Tower of Hanoi test: effects of depth of search, diagnostic subtype, and methylphenidate.

We administered the Tower of Hanoi to demographically comparable samples of control participants (n = 34) and children with the Combined (n = 22) and Inattentive subtypes (n = 19) of Attention-Deficit/Hyperactivity Disorder (ADHD). Controls excelled over children with the Inattentive subtype, who outperformed patients with the Combined subtype. These results replicated findings of greater executive deficits in the Combined than in the Inattentive type of ADHD. Double-blind administration of methylphenidate improved task performance only for patients with the Inattentive subtype. In a drug-free Baseline session, children with both subtypes of ADHD made more private verbalizations than controls, particularly when failing puzzles. In later sessions, regardless of drug condition, the inattentive sample exhibited a smaller increase in self-regulatory utterances under failure. In contrast, the combined sample decreased self-regulatory verbalizations under failure only under methylphenidate. The results support some differences between the two subtypes of ADHD in executive functioning and in their response to stimulant therapy.

Attention Deficit Disorder with Hyperactivity↗

PubMed2026

Subtype-specific clinical significance of RRM1 and RRM2 expression in non-small cell lung cancer: a TCGA-based analysis.

BACKGROUND: Non-small cell lung cancer (NSCLC), including lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC), exhibits significant molecular heterogeneity. Ribonucleotide reductase (RNR), composed of RRM1 and RRM2, is essential for DNA synthesis and repair, but its subtype-specific clinical significance in NSCLC remains unclear. OBJECTIVE: To investigate the clinical and prognostic significance of RRM1 and RRM2 expression in NSCLC, with a focus on subtype-specific differences between LUAD and LUSC. METHODS: We analyzed RNA expression and clinical data from 980 NSCLC patients in The Cancer Genome Atlas (TCGA). Associations with clinicopathologic characteristics, overall survival, and oncogenic driver alterations were assessed. RESULTS: In LUAD, high RRM2 expression was significantly associated with advanced pathologic stage (p = 0.004), nodal involvement (p = 0.005), higher T stage (p = 0.030), and gender (p = 0.046). In LUSC, RRM2 was associated with age (p = 0.008), pathologic stage (p = 0.006), and N stage (p = 0.001). RRM1 showed no significant associations with stage-related parameters in either subtype. Correlation analyses revealed modest associations between RRM1 and multiple oncogenic drivers, whereas RRM2 showed stronger subtype-specific correlations, particularly with KRAS/BRAF in LUAD and CDKN2A/SOX2 in LUSC. Kaplan-Meier analysis demonstrated that high expression of both RRM1 and RRM2 was associated with poorer overall survival in LUAD, but not in LUSC. However, neither marker remained significant after adjustment for clinicopathological variables in multivariate analysis. CONCLUSION: RRM2 is associated with tumor progression in both NSCLC subtypes, while the prognostic associations of RRM1 and RRM2 are confined to LUAD. Although neither marker demonstrated independent prognostic significance in multivariate analysis, the findings support subtype-dependent roles of RNR components and highlight the potential biological and therapeutic relevance of nucleotide metabolism pathways in LUAD.

Carcinoma, Non-Small-Cell Lung↗

PubMed1992

Muscarinic receptor subtypes in human and rat colon smooth muscle.

Muscarinic receptor subtypes in human and rat colon smooth muscle homogenates were characterized with [3H]N-methylscopolamine ([3H]NMS) by ligand binding studies. [3H]NMS saturation experiments show the existence of a homogeneous population of non-interacting binding sites with similar affinity (KD values of 1.38 +/- 0.20 nM in human colon smooth muscle and 1.48 +/- 0.47 nM in rat colon smooth muscle) and with Hill slopes close to unity in both samples of tissue. However, a significant (P less than 0.01) increase in muscarinic receptor density (Bmax) is found in human colon (29.9 +/- 2.9 fmol/mg protein) compared with rat colon (17.2 +/- 1.5 fmol/mg protein). Inhibition of [3H]NMS binding by non-labelled compounds shows the following order in human colon: atropine greater than AF-DX 116 greater than pirenzepine. Whereas in rat colon the rank order obtained is atropine greater than pirenzepine greater than AF-DX 116. Atropine and pirenzepine bind to a homogeneous population of binding sites, although pirenzepine shows higher affinity to bind to the sites present in rat colon (Ki = 1.08 +/- 0.08 microM) than those in human colon (Ki = 1.74 +/- 0.02 microM) (P less than 0.05). Similarly, IC50 values obtained in AF-DX 116 competition experiments were significantly different (P less than 0.01) in human colon (IC50 = 1.69 +/- 0.37 microM) than in rat colon (IC50 = 3.78 +/- 0.75 microM). Unlike atropine and pirenzepine, the inhibition of [3H]NMS binding by AF-DX 116 did not yield a simple mass-action binding curve (nH less than 1, P less than 0.01) suggesting the presence of more than one subtype of muscarinic receptor in both species. Computer analysis of these curves with a two binding site model suggests the presence of two populations of receptor. The apparent Ki1 value for the high affinity binding site is 0.49 +/- 0.07 microM for human colon smooth muscle and 0.33 +/- 0.05 microM for rat colon smooth muscle. The apparent Ki2 for the low affinity binding site is 8.01 +/- 1.0 microM for human samples and 6.07 +/- 1.1 microM for rat samples. These values are close enough to suggest that the first subtype of muscarinic receptor may be considered cardiac (M2) and the second subtype glandular (M3). The relative densities of the receptor subtypes are significantly different for both species. Human colon samples show the major densities of subtype M2, 22.62 +/- 1.11 fmol/mg protein, this represents 75.66 +/- 3.73% of the total receptors.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1991

Sulfhydryl reducing agents distinguish two subtypes of angiotensin II receptors in the rat brain.

Two angiotensin II receptor subtypes were distinguished in the rat brain using in vitro receptor autoradiography based on the differential effects of sulfhydryl reducing agents on 125I-sarcosine1,isoleucine8 angiotensin II binding in various brain nuclei. At several nuclei, e.g. the hypothalamus, circumventricular organs and the dorsal medulla, 125I-sarcosine1,isoleucine8 angiotensin II binding was strongly inhibited by 30 mM beta-mercaptoethanol or 5 mM dithiothreitol, whereas at other nuclei, e.g. the lateral septum, colliculi, locus coeruleus and medial amygdala, sulfhydryl reducing agents had either little effect on radioligand binding or enhanced the binding. The distribution of the sulfhydryl reducing agent inactivated subtype corresponds exactly with the distribution of DuP 753 sensitive (designated as AII alpha) 125I-sarcosine1,isoleucine8 angiotensin II binding sites25. The subtype not inhibited by sulfhydryl reducing agents corresponds with the DuP 753 insensitive (designated as AII beta) sites in the brain25. The sulfhydryl reducing agent effect on brain angiotensin II receptor subtypes is similar to that seen in angiotensin II receptor subtypes in peripheral tissues. These observations indicate that many previous studies of brain angiotensin II receptor binding that included 5 mM dithiothreitol in the assay medium overlooked the sulfhydryl reducing agent inactivated (AII alpha) receptor subtype.

Angiotensin II↗

PubMed1995

Glutamate receptor subtype expression in human postmortem brain tissue from schizophrenics and alcohol abusers.

Antibodies to functional AMPA/kainate (GluR1, GluR2, GluR3), and kainate binding sites (GluR5-7) were used as probes to characterize and quantitate glutamatergic receptor subtypes in human post-mortem brain tissue from schizophrenic subjects and non-psychotic control subjects, which included normal controls and subjects with a previous history of alcohol abuse. Crude membrane fractions from human hippocampi and cingulate cortices were fractionated by SDS-PAGE, electrotransferred to nitrocellulose, and probed for the various glutamate receptor subtypes. Western blots were developed with chemiluminescence and the images analyzed by densitometry. Significant reductions were observed in the hippocampal immunoreactivity of both GluR2 and GluR3 AMPA/kainate receptor subtypes in schizophrenic subjects compared to the entire group of non-psychotic control subjects. No significant changes were observed in schizophrenic hippocampal GluR1 and GluR5 receptor subtypes or in levels of the structural control proteins, NCAM and tau. Significant increases were observed for GluR2 and GluR3 in the hippocampi of subjects with alcohol abuse histories when compared to the non-psychotic normal control group. When subjects with alcohol abuse histories were removed from the non-psychotic control pool, schizophrenics were no longer statistically different from the remaining normal controls. An analysis of GluR2 and GluR3 immunoreactivity in the cingulate cortex revealed no changes in these receptor subtypes among any of the groups. No alterations were observed in the immunoreactivity of these various proteins due to confounding factors such as age, sex, postmortem interval, or smoking history, except in the cingulate cortex were GluR3 receptor subtype levels were significantly reduced in the brains of smokers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1994

Further characterization of human alpha 2-adrenoceptor subtypes: [3H]RX821002 binding and definition of additional selective drugs.

The characteristics of [3H]RX821002 binding to the different human alpha 2-adrenoceptor subtypes were studied on membranes from COS-7 cells transfected with the genes: alpha 2C2, alpha 2C4 and alpha 2C10. Saturation experiments indicated that the radioligand labels the three adrenoceptors with high affinity. A difference was however observed between the subtypes. The affinity of [3H]RX821002 for alpha 2C10-adrenoceptors (KD = 1.41 +/- 0.15 nM) was 3-fold higher than for alpha 2C4-adrenoceptors (KD = 4.42 +/- 0.63 nM) and 7-fold higher than for alpha 2C2-adrenoceptors (KD = 10.2 +/- 0.9 nM). Inhibition experiments with a series of 17 competitors confirmed that prazosin, oxymetazoline, WB4101, ARC239, corynanthine and chlorpromazine are subtype-selective drugs. They also demonstrated that BRL44408 and guanfacine are selective for the alpha 2C10-receptor, whereas BRL41992 and imiloxan are selective for the alpha 2C2. Given that these two latter drugs were previously shown to be specific for the alpha 2B pharmacological subtype originally defined in neonatal rat lung, these results confirm that the alpha 2C2 gene encodes for the human homolog of this receptor subtype. It is concluded that the combined use of [3H]RX821002 and of these new selective drugs may be useful for the identification of the alpha 2-adrenoceptor subtypes in human tissues.

Adrenergic alpha-Antagonists↗

PubMed1996

Subtype selectivity of a new alpha 1-adrenoceptor antagonist, JTH-601: comparison with prazosin.

The existence of alpha 1-adrenoceptors with low affinity for prazosin (alpha 1L group: alpha 1L and alpha 1N subtypes) has been proposed in addition to alpha 1-adrenoceptor subtypes with high affinity for prazosin (alpha 1H group: alpha 1A, alpha 1B and alpha 1D subtypes). A newly synthesized alpha 1-adrenoceptor antagonist, JTH-601 (N-(3-hydroxy-6-methoxy-2,4,5-trimethylbenzyl)-N-methyl-2-(4-hydro xy-2-isopropyl-5-methyl-phenoxy) ethylamine hemifumarate) showed approximately a 10 times higher affinity for the alpha 1L group, a similar affinity for the alpha 1A subtype, but a more than 10 times lower affinity for the alpha 1B and alpha 1D subtypes when compared with prazosin. These results provide a further pharmacological evidence that alpha 1-adrenoceptors with low affinity for prazosin exist in addition to those with high affinity for prazosin, suggesting that JTH-601 may be useful for characterising the alpha 1-adrenoceptor subtypes.

Adrenergic alpha-Antagonists↗