Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Muscarinic receptor subtypes in the bovine corneal epithelial cells (BCE) were characterized on the basis of their: 1) ligand binding properties, 2) linkage to Ca2+ and cAMP cell signaling pathways, and 3) gene transcripts. Receptor subtypes, m1 and m2, are indicated by competition experiments using subtype-selective muscarinic receptor ligands. [3H]N-methylscopolamine ([3H]-MS) binding was displaced with IC50s of: 1) 1 microM for the m1 antagonist, pirenzipine; 2) 51 microM for the competitive m2 antagonist, AFDX-116; 3) 100 microM for the competitive m3 antagonist, 4-DAMP. In fural2 loaded BCE, carbachol (0.001 - 100 microM) increased intracellular Ca2+ concentration ([Ca2+]i), and these responses were significantly suppressed if they were preincubated with either atropine (1 microM) or 1 microM pirenzipine. In the absence of extracellular Ca2+, these carbachol-induced increases in [Ca2+]i were depressed. A considerable fall occurred with the presence of extracellular Ca2+ and 1 microM verapamil, an L-type Ca2+ channel blocker. These responses suggest that carbachol increases Ca2+ influx through an L-type Ca2+ channel in the plasma membrane, in addition to mobilizing Ca2+ from an intracellular store. BCE also possessed muscarinic receptors which were negatively linked to cAMP production insofar as: 1) preincubation with 10 microM carbachol significantly suppressed the increases in cAMP accumulation induced by isoproterenol (1 - 25 microM); 2) this blunting effect of carbachol on cAMP production was eliminated when the BCE were preincubated with either 1 microM AFDX-116, or 100 ng/ml pertussis toxin. The results of probing for muscarinic receptor gene expression are partially consistent with the ligand binding and functional assays. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed the presence of m2 but not m1, m3 or m4 gene transcripts. In summary, we obtained pharmacological and functional evidence for m1 and m2 receptors in BCE. However, only the m2 gene transcript could be detected.
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PMID:Characterization of the muscarinic receptor subtypes in the bovine corneal epithelial cells. 887 32

The purpose of this study was to characterize the muscarinic receptor subtypes in the individual lobes of the rat prostate. Immunoprecipitation was performed on homogenates of these 3 lobes using antibodies to the m1-m4 muscarinic receptor subtypes. Reverse transcriptase polymerase chain reaction assays (RT-PCR) were also performed using primers specific for each of the five muscarinic receptor subtypes (m1-m5). The susceptibility of the receptors to degradation by endogenous prostate proteases was assessed by mixing rat ventral prostate with rat heart (m2) and rat parotid (m3) prior to immunoprecipitation. In the ventral lobe, transcripts for the m1-m4 subtypes were amplified whereas in the dorsal and lateral lobes only the m2 and m3 sets of primers amplified PCR products of the predicted size. Immunoprecipitation of the ventral lobe resulted in predominantly m3 receptors, while the majority of receptors immunoprecipitated from lateral and dorsal lobes were the m2 subtype. The m3 muscarinic subtype was apparently susceptible to degradation by prostate proteases whereas the m2 subtype was not. These results demonstrate a regional distribution in the subtypes of muscarinic receptors in the rat prostate, and a greater susceptibility of the m3 receptor to degradation during immunoprecipitation than the m2 subtype.
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PMID:Characterization of muscarinic cholinergic receptor subtypes in rat prostate. 965 83

The pharmacological and molecular properties of ATP-sensitive K(+) channels present in pig detrusor smooth muscle were investigated. In isolated pig detrusor strips, ATP-sensitive K(+) channel openers inhibited contractions elicited by low frequency field-stimulation in a concentration-dependent manner. The inhibitory effects of P1075 [N-cyano-N'-(1,1-dimethylpropyl)-N"-3-pyridylguanidine] were attenuated by glyburide with a pA(2) value of 7.38 (slope=1.08). The potency of the inhibitory effects of the K(+) channel openers on the field-stimulated contractions correlated well with those evoked by the muscarinic receptor agonist, carbachol (r=0.93) and furthermore, to relaxation of the pre-contracted (25 mM potassium chloride, KCl) human detrusor (r=0.95). Reverse transcriptase polymerase chain reaction (RT-PCR) analysis showed the presence of mRNA for sulfonylurea receptors SUR1 and SUR2B in both pig and human detrusor. Considering the similarities in the molecular and pharmacological profile of ATP-sensitive K(+) channels between the pig and the human detrusor, it is concluded that the pig detrusor may serve as a suitable in vitro model for the evaluation of novel K(+) channel openers with potential use in urological disorders in humans.
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PMID:Pharmacological and molecular analysis of ATP-sensitive K(+) channels in the pig and human detrusor. 1098 46

K+ secretion in strial marginal cells (SMC) of stria vascularis (SV) is stimulated by beta1-adrenergic receptors. The aim of the present study was to determine, whether SMC from the gerbil inner ear contain muscarinic receptors that inhibit K+ secretion. Receptors were identified with pharmacological tools in functional studies where K+ secretion was monitored as transepithelial current (Isc). The cytosolic Ca2+ concentration ([Ca2+]i) was measured as fluo-4 fluorescence and cAMP production with a colorimetric immunoassay. Further, receptors were identified in SV as transcripts by cloning and sequencing of reverse-transcriptase polymerase chain reaction (RT-PCR) products. The cholinergic receptor agonist carbachol (CCh) caused a transient increase in [Ca2+]i with a half-maximal concentration value (EC50) of (5 +/- 6) x 10(-6) m (n = 29) and a decrease in basal and stimulated cAMP production. Apical CCh had no effect on Isc but basolateral CCh caused a transient increase in Isc with an EC50 of (3 +/- 1) x 10(-6) m and a sustained decrease of Isc with an EC50 of (1.2 +/- 0.2) x 10(-5) m (n = 129). The effects of CCh on Isc and [Ca2+]i were inhibited in the presence of muscarinic antagonist 10(-6) m atropine. Further, the muscarinic antagonists pirenzipine, methoctramine and para-fluoro-hexahydo-sila-defenidol (pFHHSiD) inhibited the CCh-induced transient increase of Isc with affinity constants (KDB) of 3 x 10(-8) m (pKDB = 7.54 +/- 0.19, n = 17), 2 x 10(-6) m (pKDB = 5.71 +/- 0.26, n = 19) and 2 x 10(-8) m (pKDB = 7.65 +/- 0.28, n = 19) and the sustained decrease of Isc with KDB of 7 x 10(-8) m (pKDB = 7.05 +/- 0.09, n = 33), 6 x 10(-6) m (pKDB = 5.21 +/- 0.13, n = 23), 5 x 10(-8) m (pKDB = 7.34 +/- 0.13, n = 31), respectively. RT-PCR of total RNA isolated from SV using primers specific for the M1-M5 muscarinic receptors revealed products of the predicted sizes for the M3- and M4- but not the M1-, M2- and M5-muscarinic receptor subtypes. Sequence analysis confirmed that amplified cDNA fragments encoded gene-specific nucleotide sequences. These results suggest that K+ secretion in SMC is under the control of M3- and M4-muscarinic receptors that may be located in the basolateral membrane of strial marginal cells.
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PMID:Muscarinic receptors control K+ secretion in inner ear strial marginal cells. 1154 40