ISSN:
1432-1424
Keywords:
Chloride conductance
;
cAMP
;
Calcium
;
Ion Channel
;
Cardiac Myocytes
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
Notes:
Abstract Cl− conductance in cultured embryonic chick cardiac myocytes was characterized using whole-cell patch clamp techniques. Following elimination of cation currents in Na+and K+-free internal and external solutions, the basal whole-cell current was predominantly a Cl− current. Cl−-sensitive current (I Cl) was defined as the difference between the whole-cell currents recorded in normal and low [Cl−] o when measured in the same cell. The whole-cell current in the absence or presence of 10 μm cAMP was time independent, displayed outward rectification with the pipette [Cl−] 〈 40 mm, and was not saturated with a physiological Cl− gradient. The Cl− current was also activated by 1 μm forskolin and inhibited by 0.3 mm anthracene-9-carboxylic acid (9-AC). Forskolin was less effective than cAMP (internal dialysis) in activating the Cl− current. The cAMP- or forskolin-activated and basal Cl− current were reasonably fit by the Goldman-Hodgkin-Katz equation. The calculated P Cl in the presence of cAMP was increased by fiveto sixfold over the basal level. In the presence of 5 mm EGTA to decrease free [Ca2+] i , the whole-cell current could not be stimulated by cAMP, forskolin or IBMX (0.1 mm). These data suggest that cultured chick cardiac myocytes have a low basal Cl− conductance, which, as in some mammalian cardiac ventricular myocytes, can be activated by cAMP. However, this study shows that the activation process requires physiological free [Ca2+] i . This study was supported by grants from the National Institutes of Health (HL-17670, HL-27105 and HL-07107) for M.L. and by Institutional funds of the University of Arkansas for Medical Sciences for S.L.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00232874
Permalink