Analysis of the muscarinic receptor subtype mediating inhibition of the neurogenic contractions in rabbit isolated vas deferens by a series of polymethylene tetra-amines

1. The pharmacological characteristics of the presynaptic muscarinic receptor subtype, which mediates inhibition of the neurogenic contractions in the prostatic portion of rabbit vas deferens, have been investigated by using a series of polymethylene tetra-amines, which were selected for their ability to differentiate among muscarinic receptor subtypes. 2. It was found that all tetra-amines antagonized McN-A-343-induced inhibition in electrically stimulated rabbit vas deferens in a competitive manner and with affinity values (pA2) ranging between 6.27 ± 0.09 (spirotramine) and 8.51 ± 0.02 (AM170). 3. Competition radioligand binding studies, using native muscarinic receptors from rat tissues (M1, cortex; M2, heart; M3, submaxillary gland) or from NG 108-15 cells (M4) and human cloned muscarinic M1-M4 receptors expressed in CHO-K1 cells, were undertaken with the same tetraamines employed in functional assays. All antagonists indicated a one-site fit. 4. The affinity estimates (pKi) of tetra-amines calculated in binding assays using native receptors were similar to those obtained using cloned receptors. Among these compounds some displayed selectivity between muscarinic receptor subtypes, indicating that they may be valuable tools in receptor characterization. Spirotramine was selective for M1 receptors versus all other subtypes (pKi native: M1, 7.32 ± 0.10; M2, 6.50 ± 0.11; M3, 6.02 ± 0.13; M4, 6.28 ± 0.16; pKi cloned: M1, 7.69 ± 0.08; M2, 6.22 ± 0.14; M3, 6.11 ± 0.16; 6.35 ± 0.11) whereas CC8 is highly selective for M2 receptors versus the other subtypes (pKi native: M1 7.50 ± 0.04; M2, 9.01 ± 0.12; M3, 6.70 ± 0.08; M4, 7.56 ± 0.04; pKi cloned: M1, 7.90 ± 0.20; M2, 9.04 ± 0.08; M3, 6.40 ± 0.07; M4, 7.40 ± 0.04). Furthermore, particularly relevant for this investigation were tetra-amines dipitramine and AM172 for their ability to significantly differentiate M1 and M4 receptors. 5. The apparent affinity values (pA2) obtained for tetra-amines in functional studies using the prostatic portion of rabbit vas deferens correlated most closely with the values (pKi) obtained at either native or human recombinant muscarinic M4 receptors. This supports the view that the muscarinic receptor mediating inhibition of neurogenic contractions of rabbit vas deferens may not belong to the M1 type but rather appears to be of the M4 subtype

Inibitori delle fosfodiesterasi

Il capitolo illustra la progettazione, le proprietà chimico-fisiche, farmacocinetiche e farmacodinamiche dei principali inibitori selettivi delle fosfodiesterasi, con particolare attenzione verso gli agenti terapeutici

Corrosive Sulfur in Insulating Oils: Its Detection and Correlated Power Apparatus Failures

Contamination of paper tapes by corrosive sulfur in insulating oils may cause shorting faults between turns. Typically, this occurs at higher temperature in the upper portions of the windings of shunt reactors and power transformers. In many of the tested oils, high amounts of dibenzyl–disul?de (DBDS) were found

Rapid and Specific Determination of Contaminants, By-Products, and Additives in Insulating Mineral Oils with Tandem Mass Spectrometry

Insulating oils are often considered the life blood of electrical devices such as transformers. Proper functioning of these devices is essential for uninterrupted electrical power over long periods, often stretching into decades. To ensure longevity of insulating oils and improve certain characteristics additives are often added to the oils. On the other hand, the presence of contaminants can deteriorate the performance of the oils and can cause extensive damage to the electrical devices. To ensure optimal operation of electrical devices, additive and contaminant levels should be periodically monitored. Because of the complex chemical composition of insulating mineral oils, the determination of additives and contaminants is a difficult and often laborious task. However, the task can be made manageable with the use of current state-of-the art analytical instrumentation. This article demonstrates the use of electrospray ionization–mass spectrometry for rapid and specific determination of widely used metal deactivators Irgamet 30 and Irgamet 39. The article also presents specific quantitative determination of a highly corrosive sulfur compound dibenzyl disulfide and its principle nonsulfur by-product bibenzyl with gas chromatography and tandem mass spectrometry (GC–MS-MS)

Evaluation of the inhibitory potency of a new series of AChE-inhibitors by using a monolithic AChE-micro-IMER

The development and characterization of a human recombinant acetylcholinesterase (AChE) micro-IMER (immobilized enzyme reactor), prepared by using an in situ immobilization procedure was previously reported (1). 0.22 Units of AChE were immobilized onto a monolithic disk (12 mm in diameter and 3 mm in thickness) based on polymeric macroporous material and available under the trademark CIMÒ (Convective Interaction MediaÒ). Well-known inhibitors whose potency was distributed over four orders of magnitude were analyzed by using the AChE-IMER. Very short analysis time (2 min), absence of backpressure, low aspecific matrix interactions and immediate recovery of enzyme activity were the best characteristic of this micro-IMER. In this study the micro reactor was used to evaluate the inhibitory potency of a class of new synthesized inhibitors characterized by a polyamine backbone. The IC50 were assessed by injecting increasing concentrations of the tested inhibitor and saturating concentration of substrate. The reduction of the product area was correlated to the inhibition of the enzymatic activity by the tested inhibitor. Inhibition curves were obtained for each compound by plotting the % inhibition versus the logarithm of injected inhibitor concentration. The IC50 values obtained by micro-IMER were compared with the IC50 values calculated on the free enzyme by the Ellman’s assay and a linear correlation was found (r2 = 0.9984). The results indicate that the AChE-micro-IMER could be used for high throughput screening for new classes of inhibitors in the search for new leads. If we consider that the development of new inhibitors require a large number of compounds to be tested, the short time of analysis and very low aspecific interaction showed by this micro-IMER will allow to rapidly process hundreds of potential inhibitors