Carbostyril-based beta-adrenergic agonists: evidence for long lasting or apparent irreversible receptor binding and activation of adenylate cyclase activity in vitro

Summary The interaction of the carbostyril derivatives 5-[2-[[1-(4-aminophenyl)-2-methyl-prop-2-yl]amino]-1-hydroxyethyl]-8-hydroxycarbostyril (carbo-amine) and 5-[2[[3-[4-(bromoacetamido)phenyl]-2-methylprop-2-yl]amino]1-hydroxyethyl]-8-hydroxycarbostryril (carbo-Br) with the rat reticulocyte beta-adrenoreceptor system has been partially characterized. In the absence of a guanine nucleotide, the concentration of carbo-amine, carbo-Br and (–)isoprenaline that inhibited (–)-[¹²⁵I]iodocyanopindolol ([¹²⁵I]CYP) binding by 50% (IC₅₀) was 5.9 ± 0.2, 3.3 ± 0.3 and 49 ± 3 nM, respectively. In the presence of a guanine nucleotide, the (IC₅₀) values were carbo-amine, 21 ± 0.6 nM; carbo-Br, 7.6 ± 0.3 nM and (–)isoprenaline, 813 ± 66 nM. Preincubation of membranes with either of the carbostyril congeners followed by washing reduced specific [¹²⁵I]CYP binding capacity without changing the K _D value for the remaining receptors. The beta-antagonist nadolol largely prevented the receptor reduction induced by the carbostyril compounds. Incubation of membranes for 18 It at 25°C resulted in an 11 % recovery of the carbo-amine-induced receptor loss and no recovery of the receptors lost by preincubation with carbo-Br. However, the carbo-amine induced receptor loss could be largely reversed (80%) by membrane heating at 45°C whereas little reversal (< 10%) was observed with the carbo-Br pretreated membranes. The concentration of carbo-amine, carbo-Br and (–)isoprenaline that stimulated halt-maximal cAMP formation in reticulocyte membranes was 17.8 ± 3.1, 8.2 ± 2.1 and 241 ± 17 nM, respectively, and all 3 agonists produced the same maximal response. Initial cAMP formation stimulated by the carbostyril derivatives and (–)isoprenaline was blocked by concurrent addition of propranolol. However, the addition of propranolol after 7 min of incubation with either of the two carbostyril derivatives did not affect further cAMP production whereas with (–)isoprenaline further cAMP production was blocked. The data indicate that both carbostyril-derivatives are potent, full beta-adrenoreceptor agonists and the carbo-amine bound to the beta-adrenoreceptor in a tight, slowly dissociating manner whereas carbo-Br binding shows an apparent irreversible interaction with the receptor. Send offprint requests to S. P. Baker at the above address     

Synthesis,characterization, and antimicrobial evaluation of carbostyril derivatives of 1H-pyrazole

A new series of 12 derivatives of 4-pyrazolyl-N-arylquinoline-2,5-dione (4a–l) were synthesized by one pot base catalyzed cyclocondensation reaction of 1-aryl-5-chloro-3-methyl-1H-pyrazole-4-carbaldehyde (1a–c), Meldrum’s acid (2) and 3-arylamino-5,5-disubstitutedcyclohex-2-enone (3a–d). All the compounds were characterized by elemental analysis, FT-IR, ¹H NMR and ¹³C NMR spectral data and were screened, against six bacterial pathogens, namely Bacillus subtilis, Clostridium tetani, Streptococcus pneumoniae, Salmonella typhi, Vibrio cholerae, Escherichia coli and antifungal activity, against two fungal pathogens Aspergillus fumigatus and Candida albicans, using broth microdilution MIC (minimum inhibitory concentration) method. Some of the compounds were found to be equipotent or more potent than commercial drugs, against most of the employed strains, as evident from the screening data.     

Structure-affinity profile of 8-hydroxycarbostyril-based agonists that dissociate slowly from the β2-adrenoceptor

Several carbostyril-based β-agonists have been shown to bind tightly to and slowly dissociate from the β₂-adrenoceptor (β₂AR). In the present study, the structural features of 8-hydroxy-5-[2-[(1-phenyl-2-methylprop-2-yl)amino]-1-hydroxyethyl]-carbostyril (11a) which contribute to its binding properties at the β₂AR were investigated using a series of synthesized analogs. The k _off, estimated by the rate of cAMP decline in DDT₁ MF-2 (DDT) cells with a reduced receptor density, K _i and ligand-induced receptor reductions were determined. All of the derivatives stimulated cAMP accumulation in DDT cells in the sub to mid nanomolar range and elicited the same maximal stimulation as (–)isoproterenol. Derivatives of 11a with side chain N-substitutions comprising 2-methylbutyl, phenyl-ethyl and isopropyl had higher k _off-values and lower affinities as compared to 11a. Increasing the number of methylenes between the side chain tertiary alpha carbon and phenyl from 1 in 11a to 3 or reducing the number to 0 also resulted in derivatives with higher k _off- and K _i-values. In addition, replacement of the 8-hydroxycarbostyril nucleus of 11a with catechol reduced the affinity of the compound for the β₂AR by 48-fold and increased its k _off. Only those derivatives with the lowest k _off-values induced a decrease in the receptor density of DDT cell membranes following a preincubation and extensive washing. The data show that the 8-hydroxycarbostyril nucleus in conjunction with substitutions on the tertiary alpha carbon of the side chain and positioning of the phenyl group are important characteristics determining the high affinity and slow dissociation of 11a from the β₂AR. Received: 21 July 1998 / Accepted: 6 January 1999     

大肠埃希菌临床分离菌株喹诺酮类抗生素耐药机制研究

目的探讨我院临床分离的大肠埃希菌株耐药基因的分布及其在耐药中的作用机制。方法选择我院临床分离的大肠埃希菌菌株,采用纸片扩散法进行喹诺酮类药物药敏试验,筛选耐药菌株并测定环丙沙星MIC,对喹诺酮耐药菌株进行qnrA、qnrB、aac-（6’）-Ib-cr、GyrA及ParC检测,并进行基因扩增测序。结果 84株临床分离的大肠埃希菌菌株中有24株对喹诺酮类药物耐药,耐药率为28.4%。其中对2种药物耐药4株,对3种药物耐药6株,对5种药物耐药14株。耐药菌株MIC值为对照菌株148～596倍,24株耐药菌中检出qnrA质粒基因12株、qnrB质粒基因4株、aac-（6’）-Ib-cr基因4株、GyrA基因喹诺酮决定区突变11株、ParC基因决定区突变4株。结论我院存在大肠埃希菌喹诺酮耐药菌株,且耐药菌株耐药机制复杂,耐药基因的产生及酶类耐药突变是主要原因,临床要加强对耐药菌株的检测。