ISSN:
1432-1424
Keywords:
Patch clamp
;
Chloride channel
;
cAMP-dependent protein kinase
;
Human hematopoietic myeloblast
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract Using the inside-out patch clamp technique, we identified a Cl− channel in patches from the membrane of cultured human hematopoietic myeloblastic leukemia ML-1 cells. The Cl− channel was not seen at negative membrane potentials in excised patches until the membrane potential was depolarized to greater than +40 mV. The channel was also activated by addition of cAMP-dependent protein kinase (PKA) catalytic subunit at physiological membrane potential (−40 mV). Biophysical studies of the Cl− channel revealed that the current-voltage (I-V) relationship of the Cl− channel was outwardly rectifying in symmetrical 142 mm Cl− solutions. Single channel conductances were 48 pS for the outward current measured at +60 mV and 27 pS for the inward current at −60 mV. The open time constant of the channel was dependent on the membrane potential and was significantly prolonged at positive membrane potentials. Channels activated by cAMP-dependent protein kinase spent a significantly longer time in the open state compared to those channels activated by depolarization pulses. Pharmacological properties of the Cl− channel were also studied. Two anion transport inhibitors, anthracene-9-carboxylic acid (9-AC) and 4,4-diisothiocyanatostilbene-2,2-disulfonic acid (DIDS) caused a flickering block of the channel. Half-inhibitory concentrations (IC50) for 9-AC and DIDS were 174 ± 20 and 70±16 μm, respectively. Blockade of the Cl− channel by 9-AC or DIDS was completely reversible. Our findings suggest that outwardly rectifying Cl− channels (ORCC) are present in human hematopoietic myeloblasts. The function of ORCC may be involved in hormone-regulated cell growth, cell volume regulation and immune responses.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00233384
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