ABSTRACT
Objective To investigate the characteristics of different electrophysiology of Ca2+-activated Cl-channels (ClCa) in pulmonary arterial smooth muscle cells (PASMCs) between pulmonary arterial hypertension (PAH) rats induced by left-to-right shunt and normotensive rats,and to study its possible role in the progress of PAH induced by high pulmanry blood flow.Methods Forty SD rats were randomly divided into 3 groups:control group (n =10),sham group (n =10),PAH model group (n =20).After molding,the rats were raised in the same condition for 11 weeks.Right ventricular systolic pressure (RVSP) of each rat was measured by right cardiac catheterization procedure.Right ventricular hypertrophy index (RVHI) was calculated.Single PASMC was obtained by acute enzyme separation method and the conventional whole-cell patch clamp technique was used to record the resting membrane potential (Em),ClCa and current density.The Ⅰ-Ⅴ curve between each group were compared.Results Compared with control group and sham group,the Ⅰ-Ⅴ curve about Itail of PAH model group was significantly shift downward; the difference between control group and sham group was not significant.There were positive correlations between Em and RVSP,RVHI (all P ＜ 0.01),and negative correlations between Itail and RVSP,RVHI and Em(all P ＜ 0.01).Conclusions During the formation process of left-to-right shunt induced PAH,with the step up of pulmonary arterial pressure,the Em of PASMCs stepping up.The absolute value of current density of inward ClCa currents was increased,and its Ⅰ-Ⅴ curve was shift downward.These suggest that the change of ClCa currents may play a role in the PAH induced by left-to-right shunting.
ABSTRACT
Cystic fibrosis (CF) is an autosomal recessive disorder usually found in populations of white Caucasian descent. CF is caused by mutations in the Cystic Fibrosis Transmembrane conductance Regulator (CFTR) gene. A 5-yr-old Korean girl was admitted complaining of coughing and greenish sputum. Chest radiographs and computed tomographic (CT) scan revealed diffuse bronchiectasis in both lungs. The patient had chronic diarrhea and poor weight gain, and the abdominal pancreaticobiliary CT scan revealed atrophy of the pancreas. Finally, CF was confirmed by the repeated analysis of the quantitative pilocarpine iontophoresis test. The chloride concentration of sweat samples taken from both forearms of the pateint was an average of 88.7 mM/L (normal value <40 mM/L). After a comprehensive search for mutations in the CFTR gene, the patient was found to carry the non-synonymous L441P mutation in one allele. Molecular physiologic analysis of the L441P mutation of CFTR revealed that the L441P mutation completely abolished the CFTR Cl- channel activity by disrupting proper protein folding and membrane trafficking of CFTR protein. These results confirmed the pathogenicity of the L441P mutation of CFTR circulating in the Korean population. The possibility of CF should be suspected in patients with chronic bronchiectasis, although the frequency of CF is relatively rare in East Asia.
Subject(s)
Child, Preschool , Female , Humans , Amino Acid Substitution , Base Sequence , Cell Line , Cystic Fibrosis/diagnosis , Cystic Fibrosis Transmembrane Conductance Regulator/genetics , Lung/diagnostic imaging , Mutation , Patch-Clamp Techniques , Republic of Korea , Tomography, X-Ray ComputedABSTRACT
Objective To determine whether Ca2+ activated Cl- current(Icl(Ca)) contributes to the functional remodeling of the failing heart.Methods Whole cell patch-clamp recording technique was employed to record the Icl(Ca) in cardiac myocytes enzymatically isolatedfrom rapidly pacing induced canine failing hearts at room temperature and compared that of the normal hearts (Nor).Results Thecurrent density of DIDS(200M)sensitive Icl(Ca) induced by intracellular Ca2+ release trigged by L-type Ca2+ current(Ica,L)wassignificantly decreased in heart failare(HE)cells compared to Nor cells.At membrane voltage of 20mV,the Icl(Ca) density was 3.02±0.54 pA/pF in Nor(n=6)vs.1.31±0.25 pA/pF in HF(n=8)cells,(P＜0.01),while the averaged Ica,L density did not show differencebetween two groups.The time constant of current decay of Icl(Ca) was similar in both types of cells.On the other hand,in intra cellularCa2+ clamped mode,where the[Ca2+];was maintained at 100nmol/L,Icl(Ca) density be increased significantly in HF cells when themembrane voltage at+30mV or higher.Conclusions Our results suggest that Icl(Ca) density was decreased in pacing induced failingheart but the channel function be enhanced.Impaired Ca2+ handing in HF cells rather than reduced,Icl(Ca) channel function itself may havecaused this abnormality.The Icl(Ca) density reduction might contribute to the prolongation of action potential in failing heart.The Icl(Ca)channel function up-rugulation is likely to cause cardiac arrhythmia by inducing a delayed after depolarization,when Ca2+ overloadoccurred in diastolic failing heart cells.
ABSTRACT
Summary: The protein expression of cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-activated Cl- channel, in ovarian stimulated premature female rat ovary during a cycle of follicle development and corpus luteum formation was investigated. Animals were injected with 10 U pregnant Mare's serum gonadotropin (PMSG) and subsequently 10U hCG 48h later. Time-dependent immunohistochemistry and Western blotting experiments were performed before and 24, 48, 72h after hCG treatment. The immnnohistochemistry revealed that administration of PMSG stimulated the CFTR expression in theeal cell layer and granulosa cell layer of mature follicles 48 h post injection, coincident with the PMSG-induced peak in follicular estradiol. However, the expression of CFTR in the granuiose lutein cell layer and theeal lutein cell layer was time-dependently reduced following hCG injection, in accordance with the gradually increased progestogen level during luteum corpus formation. Western blotting analysis demonstrated that rat ovarian tissue expressed the special CFTR band at 170kD. It is concluded that cAMP-dependent Cl- channels are involved in regulation of follicle development and luteum formation.
ABSTRACT
To explore whether Cl- channel blockers interact with the ATP-sensitive K+ (KATP) channel, I have examined the effect of two common Cl- channel blockers on the KATP channel activity in isolated rat ventricular myocytes using patch clamp techniques. In inside-out patches, 4,4'-diisothio-cyanatostilbene-2,2'-disulfonic acid (DIDS) and niflumic acid applied to bath solution inhibited the KATP channel activity in a concentration-dependent manner with IC50 of 0.24 and 927 muM, respectively. The inhibitory action of DIDS was irreversible whereas that of niflumic acid was reversible. Furthermore, DIDS-induced block was not recovered despite exposure to ATP (1 mM). In cell-attached and inside-out patches, DIDS blocked the pinacidil- or 2,4-dinitrophenol (DNP)-induced KATP channel openings. In contrast, niflumic acid did not block the pinacidil-induced KATP channel openings in inside-out patches, but inhibited it in cell-attached patches. DIDS and niflumic acid produced additional block in the presence of ATP and did not affect current-voltage relationship and channel kinetics. All these results indicate that DIDS among Cl- channel blockers specifically blocks the cardiac KATP channel.