Differential sensitivity of atrial and ventricular KATP channels to metabolic inhibition

Objective: The aim is to compare the activation of ATP-sensitive potassium channels (KATP channels) in intact and metabolically impaired atrial and ventricular myocytes. Methods: The KATP channel current is measured by whole cell and gramicidin-perforated patch clamp recordings in 164 cultured neonate rat cardiomyocytes. Results: In whole cell recordings with 84 μmol/l ADP in pipette, spontaneous activity is significantly higher in atrium than ventricle, and EC50 for the KATP channel opener diazoxide is 0.13 μmol/l (atrium) versus 3.1 μmol/l (ventricle). With an ATP-regenerating system in pipette, EC50 for diazoxide is 19.7 μmol/l (atrium) versus 54.9 μmol/l (ventricle). In gramicidin-perforated patch recordings, atrial myocytes respond significantly to 100 nmol/l of the mitochondrial protonophore CCCP, while ventricular myocytes do not. EC50 for diazoxide is 129 μmol/l (atrium) versus <2500 μmol/l (ventricle) for myocytes exposed to CCCP, and 676 versus <2500 μmol/l, respectively, without CCCP. Conclusions: (1) KATP channels are significantly more sensitive to metabolic inhibition in atrial than ventricular myocytes. (2) Sensitivity of atrium versus ventricle to the channel opener diazoxide increases from 3:1 to ≥24:1 with ADP or metabolic inhibition. If extended to intact hearts, the results would predict a higher atrial sensitivity to ischemia, and a high sensitivity of the ischemic atrium to KATP channel opener

An Electrochemical Method for Making Enzyme Microsensors. Application to the Detection of Dopamine and Glutamate

International audienc

Discrimination between cystic fibrosis and CFTR-corrected epithelial cells by a membrane potential-sensitive probe

Methods to detect functional cystic fibrosis transmembrane conductance regulator (CFTR) are needed for the assessment of new therapies in cystic fibrosis (CF). We have combined patch-clamp and fluorimetric techniques to investigate whether the fluorescent voltage-sensitive probe bis-(1,3-diethylthiobarbituic anid) trimethine oxonol (Di5BAC2(3)) discriminates between changes of membrane potential (Vm evoked by cAMP in CF and CYFT-corrected epithelial cells. About 60% of the (FTR-correrced cells increased their membrane conductance and depolarized in response to cAMP, as compared to about 20% of CF cells. CFTR was found to contribute only to a fraction of the cAMP-induced responses, as indicated by the differential effects of Cl- channel blockers. Simultaneous reocording of fluorescence (AF) and membrane potential revealed that AF detected Vm changes as small as 10 mV . The relationship between deltaF and deltaVm however, was not proportional. When a large number of cells were analyzed by digital imaging, an increase in deltaF in response to cAMP was detected in the majority of CFTR-corrected cells, but only in a small proportion of CF cells. The results indicate that the DiSBAC2(3) approach is a valid tool to compare cell populations with different proportions of cells responding to CFTR arcivation by cAMP. It cannot be used, however, for quantitative assessment of functional CFTR in individual CF cells