The newly isolated peptide,urocortin(UCN)has been found to have potent cardioprotective effects.In order to investigate the effectof UCN on L-type calcium currents(ICa,L),exploring the mechanisms of UCN’s cardioprotective effects,we directly measured the ICa,Lin the adult rat cardiac myocytes exposed to UCN using standard whole-cell patch-clamp recording technique.Our results showed that UCN exerted decreasing effects on the ICa,L of the single adult rat cardiac myocytes.The current density was inhibited by about 35% after exposure of the cells to UCN(0.1 mol L−1)for 10 min,from the control value of 7.19±1.44 pA/pF to 4.74±0.75 pA/pF(n=5,P<0.05).This ICa,L-inhibiting action of UCN was concentration dependent.Moreover,no frequency dependence of UCN effects on ICa,L was observed.In combination with previous reports,our results suggest that there might be a close relationship between the cardioprotective effects of UCN and L-type calcium channels.

Azelastine is used for symptomatic relief of allergic rhinitis and asthma bronchiale.In vitro studies in smooth muscle cells from guinea pig trachea and ileum demonstrate that the drug blocks L-type Ca2+ current(Ica,L)However,for safety reasons,it is important to know whether azelastine also affects cardiac ICa,L in therapeutically relevant concentrations.We have therefore studied the effects of azelastine on ICa,L in guinea pig ventricular myocytes using standard whole-cell patch-clamp technique.Force of contraction and action potentials from isolated papillary muscles of the same species were also investigated at physiological temperature(36℃)..Azelastine (30µM).significantly reduced force of contraction,shortened action potential duration,and depressed maximum upstroke velocity.ICa,L was elicited by 200-ms-long clamp steps fromy -100 to 0 mV(one pulse every3s).Azelastine blocked ICa,L reversibly and concentration-dependently with an IC50 of 20.2±1.3µM and a Hill coefficient of 1.1.At 10µM,azelastine shifted steady-state inactivation by 5 mV Žns7.to more negative potentials.The time course of ICa,L inactivation could be described by a double exponential function.Azelastine(10µM)significantly shortened the slow inactivation time constant(Ts) from 54.2±2.8 ms under control conditions to 38.7±2.9 ms(n=16)in the presence of drug.Azelastine also reduced low-voltage-activated Ca2+ currents with a similar IC50 value(24µM,at-35mV).Since the therapeutic plasma concentrations are in the order of 10–100 nM,we conclude that azelastine does indeed affect also cardiac ICa,L,but the concentrations required are at least two orders of magnitude larger than those obtained during drug therapy.q2001 Elsevier Science B.V.All rights reserved.

Eosinophils are known to be the important effector cells in asthmatic airway inflammation.The purpose of this study was to investigate the effects of nobiletin,a polymethoxyflavonoid,on eosinophilic airway inflammation of asthmatic rats,and explore its possible mechanisms.Animals were actively sensitized by subcutaneous injection of ovalbumin(OVA).The inflammation in lung tissues of asthmatic rats was observed by hematoxylin and eosin(HE)staining.The eosinophils in blood and BALF were separated by Percoll density gradient centrifugation and counted under microscope.The level of Eotaxin was detected by enzyme-linked immunosorbent assay(ELISA).In addition,the apoptosis of eosinophils was labeled by TdT-mediated dUTP nick end labeling(TUNEL)technique,the semi-quantitative detection for Fas mRNA expression of eosinophils was performed by reverse transcription-polymerase chain reaction(RT-PCR).The airway inflammation of asthmatic rats pretreated with nobiletin was obviously alleviated.Nobiletin(1.5 and 5.0 mg/kg given intraperitoneally)significantly reduced OVA-induced increases in eosinophils,remarkably lowered the level of Eotaxin in blood and broncho-alveolar lavage fluid(BALF)of asthmatic rats.On the other hand,semi-quantitative RT-PCR analysis for Fas of eosinophils from OVA aerosol-challenged sensitized rats showed that Fas mRNA expression of eosinophils was obviously enhanced by nobiletin.Meanwhile,the apoptosis index of cultured eosinophils was significantly elevated after treatment with different doses of nobiletin.These results indicated that nobiletin could inhibit the eosinophilic airway inflammation.Lowering the levels of Eotaxin,relieving airway infiltration of eosinophils and promoting apoptosis of eosinophils by enhancing expression of Fas mRNA may be important mechanisms for nobiletin to antagonize eosinophilic airway inflammation of asthmatic rats.D 2005 Elsevier Inc.All rights reserved.